(Document)

n1.doc

1. 
   Introduction
2. 
   Main part

1. 
   The history of the development of communication lines
2. 
   Design and characteristics of optical communication cables
   1. 
      
   2. 
      Optical fibers and features of their manufacture
   3. 
      Optical cable designs
3. 
   Basic requirements for communication lines
4. 
   Advantages and disadvantages of optical cables
5. 
   

1. 
   Output
2. 
   Bibliography

Introduction
Today, as never before, the regions of the CIS countries need communication, both quantitatively and qualitatively. Regional leaders are primarily concerned about social dimension this problem, because the phone is a basic necessity. Communication also affects economic development region, its investment attractiveness. At the same time, telecommunication operators, spending a lot of effort and resources to support a decrepit telephone network, still seek funds to develop their networks, to digitize, and introduce fiber-optic and wireless technologies.

At this point in time, a situation has developed when practically all the largest Russian departments are carrying out a large-scale modernization of their telecommunication networks.

Over the last period of development in the field of communications, the most widespread are optical cables (OC) and fiber-optic transmission systems (FOTS), which by their characteristics are much superior to all traditional cables of the communication system. Communication over fiber-optic cables is one of the main directions of scientific and technological progress. Optical systems and cables are used not only for organizing urban and long-distance telephone communications, but also for cable television, video telephony, radio broadcasting, computer technology, technological communications, etc.

Using fiber-optic communication, the volume of transmitted information dramatically increases in comparison with such widespread means as satellite communication and radio-relay lines, this is due to the fact that fiber-optic transmission systems have a wider bandwidth.

For any communication system, three factors are important:

The information capacity of the system, expressed in the number of communication channels, or the information transfer rate, expressed in bits per second;

Attenuation, which determines the maximum length of the regeneration section;

Resistance to environmental influences;

The most important factor in the development of optical systems and communication cables was the emergence of optical quantum generator- laser. The word laser is made up of the first letters of the phrase Light Amplification by Emission of Radiation - amplification of light using induced radiation. Laser systems operate in the optical wavelength range. If transmission over cables uses frequencies - megahertz, and over waveguides - gigahertz, then for laser systems the visible and infrared spectrum of the optical wavelength range (hundreds of gigahertz) is used.

The guiding system for fiber-optic communication systems are dielectric waveguides, or fibers, as they are called because of their small transverse dimensions and method of production. At the time when the first fiber was produced, the attenuation was of the order of 1000 dB / km, this was due to losses due to various impurities present in the fiber. In 1970, optical fibers with an attenuation of 20 dB / km were created. The core of this fiber was made of quartz with an addition of titanium to increase the refractive index, and pure quartz served as a cladding. In 1974. attenuation was reduced to 4 dB / km, and in 1979. Fibers with an attenuation of 0.2 dB / km at a wavelength of 1.55 μm have been obtained.

Advances in low-loss fiber technology have stimulated work on the creation of fiber-optic communication lines.

Fiber-optic communication lines have the following advantages over conventional cable lines:

High noise immunity, insensitivity to external electromagnetic fields and virtually no crosstalk between individual fibers laid together in a cable.

Significantly higher bandwidth.

Low weight and dimensions. That reduces the cost and time of laying the optical cable.

Complete electrical isolation between the input and output of the communication system, so a common ground for the transmitter and receiver is not required. You can repair the optical cable without turning off the equipment.

No short circuits, as a result of which fiber optic fibers can be used to cross hazardous areas without fear of short circuits, which can cause a fire in areas with combustible and flammable media.

Potentially low cost. Although fiber optic fibers are made from ultra-clear glass with impurities of less than a few parts per million, they are not very expensive in mass production. In addition, the production of light guides does not use such expensive metals as copper and lead, the reserves of which are limited on Earth. The cost of electric lines of coaxial cables and waveguides is constantly increasing both with a shortage of copper and with an increase in the cost of energy costs for the production of copper and aluminum.

There has been tremendous progress in the development of fiber-optic communication lines (FOCL) in the world. Currently, fiber-optic cables and transmission systems for them are produced in many countries around the world.

Special attention in our country and abroad is paid to the creation and implementation of single-mode transmission systems over optical cables, which are considered as the most promising direction in the development of communication technology. The advantage of single-mode systems is the ability to transmit a large flow of information over the required distances at long lengths of regeneration sections. There are already fiber-optic lines at big number channels with a regeneration section length of 100 ... 150 km. Recently, 1.6 million km are produced annually in the USA. optical fibers, and 80% of them are in a single-pod version.

Modern domestic second-generation fiber-optic cables have been widely used, the production of which has been mastered by the domestic cable industry, these include cables of the following type:

OKK - for urban telephone networks;

OKZ - for intrazonal;

OKL - for backbone communication networks;

Fiber-optic transmission systems are used in all sections of the primary VSS network for backbone, zonal and local communications. The requirements for such transmission systems differ in the number of channels, parameters and technical and economic indicators.

On the backbone and zonal networks, digital fiber-optic transmission systems are used, on local networks, digital fiber-optic transmission systems are also used to organize connecting lines between automatic telephone exchanges, and on the subscriber section of the network, both analog (for example, for organizing a television channel) and digital transmission systems can be used. ...

The maximum length of line paths of trunk transmission systems is 12,500 km. With an average length of about 500 km. The maximum length of the linear paths of the transmission systems of the intra-zone primary network can be no more than 600 km. With an average length of 200 km. The maximum length of urban connecting lines for various transmission systems is 80 ... 100 km.
A person has five senses, but one of them is especially important - this is vision. Through the eyes, a person perceives most there is 100 times more information about the world around him than through hearing, not to mention touch, smell and taste.

used fire and then various types of artificial light sources to give signals. Now in the hands of man was both a light source and the process of modulating light. He actually built what today we call an optical communication line, or optical communication system, comprising a transmitter (source), a modulator, an optical cable line, and a receiver (eye). Having defined the transformation of a mechanical signal into an optical signal as modulation, for example, opening and closing a light source, we can observe the reverse process in the receiver - demodulation: the conversion of an optical signal into a signal of another kind for further processing in the receiver.

Such treatment may represent, for example, the transformation

light image in the eye in a sequence of electrical impulses

the human nervous system. The brain is included in the processing as the last link in the chain.

Another very important parameter used when transmitting messages is the modulation rate. The eye has limitations in this respect. He is well adapted to the perception and analysis of complex pictures of the surrounding world, but he cannot follow simple fluctuations in brightness when they follow faster than 16 times per second.

The history of the development of communication lines

Communication lines arose simultaneously with the advent of the electric telegraph. The first communication lines were cable. However, due to the imperfect design of cables, underground cable communication lines soon gave way to overhead ones. The first long-distance air line was built in 1854 between St. Petersburg and Warsaw. In the early 70s of the last century, an overhead telegraph line was built from St. Petersburg to Vladivostok with a length of about 10 thousand km. In 1939, the world's longest high-frequency telephone trunk line Moscow-Khabarovsk with a length of 8300 km was put into operation.

The creation of the first cable lines is associated with the name of the Russian scientist P.L.Schilling. Back in 1812, Schilling in St. Petersburg demonstrated the explosions of sea mines, using for this purpose an insulated conductor he had created.

In 1851, simultaneously with the construction of the railway between Moscow and St. Petersburg, a telegraph cable was laid, insulated with gutta-percha. The first submarine cables were laid in 1852 through the Northern Dvina and in 1879 across the Caspian Sea between Baku and Krasnovodsk. In 1866, a cable transatlantic telegraph communication line between France and the United States was put into operation,

In 1882-1884. the first urban telephone networks in Russia were built in Moscow, Petrograd, Riga, Odessa. In the 90s of the last century, the first cables with up to 54 cores were suspended on the city telephone networks of Moscow and Petrograd. In 1901, the construction of the underground city telephone network began.

The first designs of communication cables, dating back to the beginning of the 20th century, made it possible to carry out telephone transmission over short distances. These were the so-called city telephone cables with air-paper insulation of cores and twisting them in pairs. In 1900-1902. A successful attempt was made to increase the transmission distance by artificially increasing the inductance of cables by including inductors into the circuit (Pupin's proposal), as well as using conductive cores with a ferromagnetic winding (Krarup's proposal). Such methods at that stage made it possible to increase the range of telegraph and telephone communications several times.

An important stage in the development of communication technology was the invention, and since 1912-1913. mastering the production of electronic tubes. In 1917, V. I. Kovalenkov developed and tested on the line a telephone amplifier based on electronic tubes. In 1923, telephone communication with amplifiers was established on the Kharkov-Moscow-Petrograd line.

The development of multichannel transmission systems began in the 1930s. Subsequently, the desire to expand the spectrum of transmitted frequencies and increase the capacity of lines led to the creation of new types of cables, the so-called coaxial. But their mass production refers only to 1935, at the time of the appearance of new high-quality dielectrics such as escapon, high-frequency ceramics, polystyrene, styroflex, etc. long distance programs. The first coaxial line for 240 HF telephony channels was laid in 1936. The first transatlantic submarine cables, laid in 1856, were used only for telegraph communication, and only 100 years later, in 1956, an underwater coaxial trunk line was built between Europe and America for multichannel telephony.

In 1965-1967. experimental waveguide communication lines for the transmission of broadband information appeared, as well as cryogenic superconducting cable lines with very low attenuation. Since 1970, work has been actively developed to create light guides and optical cables using visible and infrared radiation in the optical wavelength range.

The development of an optical fiber and the production of cw generation of a semiconductor laser played a decisive role in the rapid development of fiber-optic communication. By the early 1980s, fiber-optic communication systems had been developed and tested in real conditions. The main areas of application of such systems are the telephone network, cable television, intra-facility communications, computer technology, monitoring and control systems for technological processes, etc.

Urban and intercity fiber-optic communication lines have been laid in Russia and other countries. They are assigned a leading place in the scientific and technological progress of the communications industry.
Design and characteristics of optical communication cables
Varieties of optical communication cables

An optical cable consists of silica glass optical fibers (optical fibers) twisted in a certain system, enclosed in a common protective sheath. If necessary, the cable can contain power (reinforcing) and damping elements.

Existing OK, according to their purpose, can be classified into three groups: trunk, zonal and urban. Underwater, object and assembly OKs are allocated into separate groups.

Trunk OK are intended to transmit information over long distances and a significant number of channels. They should have low attenuation and dispersion and high data throughput. A single-mode fiber with core and cladding dimensions 8/125 microns is used. Wavelength 1.3 ... 1.55 μm.

Zonal OKs are used to organize multichannel communication between the regional center and districts with a communication range of up to 250 km. Gradient fibers with a size of 50/125 microns are used. Wavelength 1.3 μm.

Urban OK are used as connecting lines between city automatic telephone exchanges and communication centers. They are designed for short distances (up to | 10 km) and a large number of channels. Fibers - gradient (50/125 microns). Wavelengths 0.85 and 1.3 μm. These lines generally operate without intermediate line regenerators.

Underwater OCs are designed to communicate across large water obstacles. They must have high mechanical tensile strength and have reliable moisture resistant coatings. It is also important for subsea communications to have low attenuation and long regeneration lengths.

Object OK are used to transfer information within an object. This includes office and video telephone communications, an internal cable television network, as well as on-board information systems of mobile objects (aircraft, ships, etc.).

Mounting OK are used for intra- and inter-unit installation of equipment. They are made in the form of bundles or flat strips.
Optical fibers and features of their manufacture

The main element of the OC is an optical fiber (light guide) made in the form of a thin glass fiber of a cylindrical shape, through which light signals with wavelengths of 0.85 ... 1.6 μm are transmitted, which corresponds to the frequency range (2.3 ... 1 , 2) 10 14 Hz.

The light guide has a two-layer structure and consists of a core and a cladding with different refractive indices. The core is used to transmit electromagnetic energy. The purpose of the cladding is to create better reflection conditions at the core-cladding interface and to protect against interference from the surrounding space.

The core of the fiber, as a rule, consists of silica, and the cladding can be silica or polymer. The first fiber is called quartz-quartz, and the second is quartz-polymer (silicon-organic compound). Based on the physical and optical characteristics, preference is given to the first one. Quartz glass has the following properties: refractive index 1.46, thermal conductivity coefficient 1.4 W / mk, density 2203 kg / m 3.

Outside the fiber is a protective coating to protect it from mechanical stress and color application. The protective coating is usually made in two layers: first, an organosilicon compound (SIEL), and then epoxydrylate, fluoroplastic, nylon, polyethylene or varnish. Total fiber diameter 500 ... 800 μm

Three types of optical fibers are used in the existing optical fiber structures: stepped with a core diameter of 50 μm, gradient with a complex (parabolic) profile of the refractive index of the core, and single-mode with a thin core (6 ... 8 μm)
In terms of frequency bandwidth and transmission range, single-mode fibers are the best, and stepped ones are the worst.

The most important problem of optical communication is the creation of optical fibers (OF) with low losses. Quartz glass is used as a starting material for the production of optical fiber, which is a good medium for the propagation of light energy. However, as a rule, glass contains a large amount of foreign impurities such as metals (iron, cobalt, nickel, copper) and hydroxyl groups (OH). These impurities lead to a significant increase in losses due to absorption and scattering of light. To obtain an optical fiber with low losses and attenuation, it is necessary to get rid of impurities so that the glass is chemically pure.

At present, the most widespread method of creating an OM with low losses by chemical vapor deposition.

The production of OM by chemical vapor deposition is carried out in two stages: a two-layer quartz preform is made and a fiber is drawn from it. The workpiece is manufactured as follows
A jet of chlorinated quartz and oxygen is fed into a hollow quartz tube with a refractive index 0.5 ... 2 m long and 16 ... 18 mm in diameter. As a result chemical reaction at a high temperature (1500 ... 1700 ° C), pure quartz is deposited in layers on the inner surface of the tube. Thus, the entire inner cavity of the tube is filled, except for the very center. To eliminate this air channel, an even higher temperature (1900 ° C) is applied, due to which collapse occurs and the tubular billet turns into a solid cylindrical billet. The pure precipitated quartz then becomes an RI core with a refractive index , and the tube itself acts as a shell with a refractive index . Fiber extraction from the workpiece and its winding on the receiving drum are carried out at the glass softening temperature (1800 ... 2200 ° C). More than 1 km of optical fiber is obtained from a 1 m long workpiece.
The advantage of this method is not only the production of an optical fiber with a core of chemically pure quartz, but also the possibility of creating gradient fibers with a given refractive index profile. This is done: through the use of doped quartz with an addition of titanium, germanium, boron, phosphorus or other reagents. The refractive index of the fiber can vary depending on the additive used. So, germanium increases and boron decreases the refractive index. By selecting the formulation of doped quartz and observing a certain amount of additive in the layers deposited on the inner surface of the tube, it is possible to provide the required character of change over the cross section of the fiber core.

Optical cable designs

OK designs are mainly determined by the purpose and scope of their application. In this regard, there are many design options. A large number of cable types are currently being developed and manufactured in various countries.

However, all the variety of existing types of cables can be divided into three groups

1. 
   concentric twisted cables
2. 
   shaped core cables
3. 
   flat ribbon cables.

The cables of the first group have a traditional concentric twisting of the core by analogy with electric cables. Each subsequent twist of the core has six more fibers than the previous one. Such cables are known mainly with the number of fibers 7, 12, 19. Most often, the fibers are located in separate plastic tubes, forming modules.

The cables of the second group have a shaped plastic core with grooves in the center, in which the optical fiber is placed. The grooves and, accordingly, the fibers are located along the helicoid, and therefore they do not experience longitudinal tensile stress. These cables can contain 4, 6, 8 and 10 fibers. If it is necessary to have a large cable capacity, then several primary modules are used.

A ribbon cable consists of a stack of flat plastic strips, into which a certain number of optical fibers are mounted. Most often, a tape contains 12 fibers, and the number of tapes is 6, 8 and 12. With 12 tapes, such a cable can contain 144 fibers.

In optical cables except for ОВ , as a rule, there are the following elements:

• 
  power (hardening) rods, taking on a longitudinal load, to break;
• 
  fillers in the form of continuous plastic filaments;
• 
  reinforcing elements that increase the durability of the cable under mechanical stress;
• 
  outer protective sheaths that protect the cable from moisture, vapors of harmful substances and external mechanical influences.

French-made OKs are of interest. They, as a rule, are completed from unified modules consisting of a plastic rod 4 mm in diameter with ribs along the perimeter and ten OVs located along the periphery of this rod. The cables contain 1, 4, 7 of these modules. Outside, the cables have an aluminum and then a polyethylene sheath.
The American cable, widely used in GTS, is a stack of flat plastic strips containing 12 OV each. The cable can have from 4 to 12 tapes containing 48 to 144 fibers.

In England, an experimental power transmission line with phase wires containing OV for technological communication along the power transmission line was built. In the center of the power line wire there are four OVs.

Suspended OK are also used. They have a metal cable embedded in the cable jacket. The cables are intended for suspension on overhead line supports and building walls.

For underwater communications, OCs are designed, as a rule, with an outer armor covering made of steel wires (Fig. 11). In the center there is a module with six OBs. The cable has a copper or aluminum tube. The pipe-to-water circuit supplies the remote power supply current to the subsea maintenance-free amplifying points.

Basic requirements for communication lines

In general terms, the requirements of highly developed modern telecommunication technology to long-distance communication lines can be formulated as follows:

• 
  communication over distances up to 12,500 km within the country and up to 25,000 for international communication;
• 
  broadband and suitability for the transmission of various types of modern information (television, telephony, data transmission, broadcasting, transmission of newspaper strips, etc.);
• 
  protection of chains from mutual and external interference, as well as from thunderstorms and corrosion;
• 
  stability of electrical parameters of the line, stability and reliability of communication;
• 
  the efficiency of the communication system as a whole.

In accordance with this, cable technology is developing in the following directions:

• 
  The predominant development of coaxial systems that allow organizing powerful communication beams and the transmission of television programs over long distances via a single-cable communication system.
• 
  Creation and implementation of promising communication channels that provide a large number of channels and do not require scarce metals (copper, lead) for their production.
• 
  Widespread introduction of plastics (polyethylene, polystyrene, polypropylene, etc.) into cable technology, which have good electrical and mechanical characteristics and allow you to automate production.
• 
  Introduction of aluminum, steel and plastic casings instead of lead ones. The sheaths must be airtight and ensure the stability of the electrical parameters of the cable during the entire service life.
• 
  Development and introduction into production of cost-effective designs of intra-zone communication cables (single-coaxial, one-quadruple, armored).
• 
  Creation of shielded cables that reliably protect the information transmitted through them from external electromagnetic influences and thunderstorms, in particular, cables in two-layer sheaths such as aluminum - steel and aluminum - lead.
• 
  Increasing the dielectric strength of the insulation of communication cables. A modern cable must simultaneously possess the properties of both a high-frequency cable and a power electric cable, and ensure the transmission of high voltage currents for remote power supply of unattended amplifying points over long distances.

Along with saving non-ferrous metals, and primarily copper, optical cables have the following advantages:

• 
  broadband, the ability to transmit a large flow of information (several thousand channels);
• 
  small losses and, accordingly, large lengths of translation sections (30 ... 70 and 100 km);
• 
  small overall dimensions and weight (10 times less than electric cables);
• 
  high immunity from external influences and transient interference;
• 
  reliable safety technology (no sparks and short circuits).

The disadvantages of optical cables include:

• 
  exposure of optical fibers to radiation, due to which dark spots appear and attenuation increases;
• 
  hydrogen corrosion of glass, leading to microcracks in the fiber and deterioration of its properties.

Advantages and Disadvantages of Fiber Optic Communication
Advantages of open communication systems:

1. 
   Higher ratio of received signal power to radiated power at smaller apertures of the transmitter and receiver antennas.
2. 
   Better spatial resolution with smaller transmitter and receiver antenna apertures
3. 
   Very small dimensions of the transmitting and receiving modules used for communication over distances of up to 1 km
4. 
   Good communication secrecy
5. 
   Mastering the unused portion of the spectrum of electromagnetic radiation
6. 
   No need to obtain a permit to operate the communication system

Disadvantages of open communication systems:

1. 
   Low suitability for radio broadcasting due to the high directivity of the laser beam.
2. 
   High required pointing accuracy of transmitter and receiver antennas
3. 
   Low efficiency of optical emitters
4. 
   Relatively high level noise in the receiver, due in part to the quantum nature of the optical signal detection process
5. 
   Influence of atmospheric characteristics on communication reliability
6. 
   Possibility of hardware failures.

Advantages of guiding communication systems:

1. 
   The possibility of obtaining light guides with low attenuation and dispersion, which makes it possible to make large distances between repeaters (10 ... 50 km)
2. 
   Small diameter single fiber cable
3. 
   The admissibility of bending the fiber at small radii
4. 
   Low weight of optical cable with high information bandwidth
5. 
   Low cost of fiber material
6. 
   Possibility of obtaining optical cables without electrical conductivity and inductance
7. 
   Negligible crosstalk

1. 
   High communication stealth: signal splitting is only possible when directly connected to a separate fiber
2. 
   Flexibility in the implementation of the required bandwidth: fiber types of various types allow you to replace electrical cables in digital communication systems of all hierarchy levels
3. 
   Possibility of continuous improvement of the communication system

Disadvantages of guiding communication systems:

1. 
   Difficulty connecting (splicing) optical fibers
2. 
   The need to lay additional conductive conductors in an optical cable to provide power to remotely controlled equipment
3. 
   Sensitivity of an optical fiber to water when it enters the cable
4. 
   Optical fiber sensitivity to ionizing radiation
5. 
   Low efficiency of optical radiation sources with limited radiation power
6. 
   Difficulties in implementing the multiple-station (parallel) access mode using a time-division bus
7. 
   High noise level in the receiver

Directions of development and application of fiber optics

Wide horizons have opened up for the practical application of OC and fiber-optic transmission systems in such sectors of the national economy as radio electronics, informatics, communications, computing, space, medicine, holography, mechanical engineering, nuclear power, etc. Fiber optics is developing in six directions:

1. 
   multichannel information transmission systems;
2. 
   cable TV;
3. 
   local area networks;
4. 
   sensors and systems for collecting information processing and transmission;
5. 
   communication and telemechanics on high-voltage lines;
6. 
   equipment and installation of mobile objects.

The use of optical systems in cable television provides high image quality and significantly expands the possibilities of information services for individual subscribers. In this case, a custom reception system is implemented and subscribers are given the opportunity to receive images of newspaper strips, magazine pages and reference data from the library and training centers on their TV screens.

On the basis of OK, local computer networks of various topologies (ring, star, etc.) are created. Such networks make it possible to combine computing centers into a single information system with high bandwidth, high quality and security against unauthorized access.

Recently, a new direction has appeared in the development of fiber-optic technology - the use of the mid-infrared wavelength range of 2 ... 10 microns. It is expected that the loss in this range will not exceed 0.02 dB / km. This will allow communication over long distances with regeneration sections up to 1000 km. The study of fluoride and chalcogenide glasses with additions of zirconium, barium and other compounds with super-transparency in the infrared wavelength range makes it possible to further increase the length of the regeneration section.

New interesting results are expected in the use of nonlinear optical phenomena, in particular, the salt-ton regime of propagation of optical pulses, when the pulse can propagate without changing its shape or periodically change its shape during propagation along the fiber. The use of this phenomenon in optical fibers will significantly increase the volume of transmitted information and the communication range without the use of repeaters.

It is very promising to implement in FOCL the method of frequency separation of channels, which consists in the fact that radiation from several sources operating at different frequencies is simultaneously introduced into the fiber, and at the receiving end, using optical filters, the signals are separated. This method of channel separation in fiber-optic communication lines is called wavelength division multiplexing or multiplexing.

When building subscriber networks of fiber-optic communication lines, except traditional structure the telephone network of the radial-node type provides for the organization of ring networks, providing savings in cable.

It can be assumed that in the second generation FOTS, amplification and transformation of signals in regenerators will occur at optical frequencies using integrated optics elements and circuits. This will simplify the circuits of regenerative amplifiers, improve their efficiency and reliability, and reduce the cost.

In the third generation of FOTS, it is proposed to use the conversion of speech signals into optical signals directly using acoustic transducers. An optical telephone has already been developed and work is underway to create fundamentally new automatic telephone exchanges that commute light rather than electrical signals. There are examples of creating multi-position high-speed optical switches that can be used for optical switching.

On the basis of OK and digital transmission systems, an integral multipurpose network is created, including various types of information transmission (telephony, television, computer and ACS data transmission, video telephone, phototelegraph, transmission of newspaper strips, messages from banks, etc.). A digital PCM channel with a transmission rate of 64 Mbit / s (or 32 Mbit / s) was adopted as a unified one.

For widespread use of QA and FOTS, it is necessary to solve a number of problems. These primarily include the following:

• 
  elaboration of systemic issues and determination of technical and economic indicators of the use of OK in communication networks;
• 
  mass industrial production of single-mode fibers, light guides and cables, as well as optoelectronic devices for them;
• 
  increasing the moisture resistance and reliability of OK due to the use of metal shells and hydrophobic filling;
• 
  mastering the infrared wavelength range of 2 ... 10 microns and new materials (fluoride and chalcogenide) for the manufacture of optical fibers that allow communication over long distances;
• 
  creation of local networks for computer technology and informatics;
• 
  development of test and measuring equipment, reflectometers, testers necessary for the production of OK, setting up and operating fiber-optic communication lines;
• 
  mechanization of laying technology and automation of installation of OK;
• 
  improvement of the technology of industrial production of optical fibers and optical fiber, reduction of their cost;
• 
  research and implementation of the soliton transmission mode, in which the pulse is compressed and the dispersion is reduced;
• 
  development and implementation of a system and equipment for spectral multiplexing OK;
• 
  creation of an integrated subscriber network for multipurpose purposes;
• 
  creation of transmitters and receivers that directly convert sound into light and light into sound;
• 
  increasing the degree of integration of elements and the creation of high-speed nodes of channel-forming PCM equipment with the use of integrated optics elements;
• 
  creation of optical regenerators without converting optical signals into electrical ones;
• 
  improvement of transmitting and receiving optoelectronic devices for communication systems, mastering coherent reception;
• 
  development of effective methods and devices for power supply of intermediate regenerators for zonal and backbone communication networks;
• 
  optimization of the structure of various sections of the network, taking into account the peculiarities of the use of systems at the OK;
• 
  improvement of equipment and methods for frequency and time separation of signals transmitted through optical fibers;
• 
  development of a system and devices for optical switching.

Output
At present, wide horizons have opened up for the practical application of OC and fiber-optic transmission systems in such sectors of the national economy as radio electronics, computer science, communications, computing, space, medicine, holography, mechanical engineering, nuclear power, etc.

Fiber optics is developing in many directions and without it modern production and life are not possible.

The use of optical systems in cable television provides high image quality and significantly expands the possibilities of information services for individual subscribers.

Fiber optic sensors are capable of operating in hostile environments, are reliable, small-sized and not subject to electromagnetic influences. They make it possible to evaluate various physical quantities (temperature, pressure, current, etc.) at a distance. The sensors are used in the oil and gas industry, security and fire alarm systems, automotive equipment, etc.

It is very promising to use OC on high-voltage power transmission lines (PTL) for the organization of technological communication and telemechanics. Optical fibers are embedded in a phase or cable. Here, the channels are highly protected from the electromagnetic effects of power lines and thunderstorms.

Lightness, small size, non-flammability OK made them very useful for installation and equipment aircraft, ships and other mobile devices.
Bibliography

1. 
   Optical communication systems / J. Gower - M .: Radio and communication, 1989;
2. 
   Communication lines / I. I. Grodnev, S. M. Vernik, L. N. Kochanovsky. - M .: Radio and communication, 1995;
3. 
   Optical cables / I. I. Grodnev, Yu. T. Larin, I. I. Teumen. - M .: Energoizdat, 1991;
4. 
   Optical cables of multichannel communication lines / A. G. Muradyan, I. S. Goldfarb, V. N. Inozemtsev. - M .: Radio and communication, 1987;
5. 
   Fiber light guides for information transmission / J.E. Midwinter. - M .: Radio and communication, 1983;
6. 
   Fiber-optic communication lines / I. I. Grodnev. - M .: Radio and communication, 1990

The degree of development of a society is largely determined by the state of telecommunications (telecommunications).

Telecommunications provides radiation, transmission and reception of signs, written text, images and sounds, messages and signals of any kind via wires, radio, optical or other electromagnetic systems. In telecommunications, they operate with an electrical signal, therefore, to transmit messages (speech, music, texts, documents, images of moving and stationary objects) over a distance (or for recording on a magnetic tape, optical disc), they must be converted into electrical signals, i.e. into electromagnetic vibrations. Without telecommunications, it is impossible to imagine not only industry, science, defense, but also human life. Even the most valuable information is useless if there are no communication channels to transmit and receive it. The number of only household electronic devices produced in the world has long exceeded the number of inhabitants on the planet. And this despite the fact that telecommunications, computer technology and radio electronics have developed mainly in the last 50 years, many types of communication systems and household devices have appeared in the last decade, and some - literally in recent years.

If transport is a means for moving goods and people, then telecommunication systems and networks are "transport" for "transporting" any information by means of electromagnetic waves. However, if the first type of transport is in plain sight and therefore in the center of attention, then the second is mostly hidden and to the majority seems to be some kind of simple means of transmitting telegrams or conducting telephone conversations. After all, no one thinks (excluding specialists) how hundreds of thousands of transmitters of medium and high power and more than a billion low power can simultaneously work, how with the help of a miniature mobile device it is possible to transmit speech, data, images (so far of medium definition) to almost anywhere on our planet, determine your location and make the necessary computer calculations.

Each of the directions in the development of message transmission technology (telegraphy, telephony, data transmission, facsimile communication, television, sound broadcasting, etc.) and devices for their reception (telegraphs, telephones, faxes, televisions, radios, etc.) has its own history of invention, creation and operation. The names of many inventors are known, but in a number of cases it is difficult to ascribe to someone alone the primacy in the invention of certain technical means of transmitting and receiving messages. Let us note only the most outstanding milestones in the development of these areas of technology.

In 1792, the first semaphore signal transmission line was built (by the French inventors brothers K. and I. Chappe), connecting Paris and Lille (225 km). The signal traveled all the way in 2 minutes. The device for transmitting messages was called "tachygraph" (literally cursive writer), and later - "telegraph".

The optical telegraph was a chain of towers located on the tops of the hills, at a line-of-sight distance. Each tower was equipped with a vertical pillar with three fixed crossbeams: one long horizontal one and two short ones, movably attached to its ends. With the help of special mechanisms, the crossbeams changed their position so that 92 different shapes could be formed. Chappe selected 8,400 of the most frequently used words and arranged them in the codebook on 92 pages of 92 words each. From tower to tower, first the page number was transmitted, and then the number of the word on it.

Chapp's telegraph was widespread in the 19th century. In 1839–54. the world's longest optical telegraph line Petersburg - Warsaw (149 stations, 1200 km) operated. Through it, a telegram containing 100 symbol signals was transmitted in 35 minutes. Optical telegraphs of various designs have been in operation for about 60 years, although they did not provide (due to weather conditions) high reliability and reliability.

The discoveries in the field of electricity contributed to the fact that gradually the telegraph from optical to electrical. In 1832, the Russian scientist P.L.Schilling demonstrated in St. Petersburg the world's first practically usable electromagnetic telegraph. The first such lines of communication provided transmission of 30 words per minute. A significant contribution to this area was made by the American inventor S. Morse (in 1837 he proposed the code

- Morse code, and in 1840. created a self-searching apparatus, which was then used on telegraph lines of all countries for more than a hundred years), the Russian scientist B.S. Jacobi (in 1839 he proposed a direct-printing apparatus, in 1840 - an electrochemical recording method), the English physicist D. Hughes (in 1855 developed an original version of an electromechanical direct-printing apparatus), German electrical engineer and entrepreneur E. Siemens (in 1844 improved B.S. Jacobi's apparatus), French inventor J. Baudot (in 1874 proposed a method of transmitting several signals over one physical line - temporary sealing; the greatest practical distribution was received by Bodo's devices for double telegraphy, which operated almost until the middle of the 20th century at a speed of 760 characters per minute, in honor of Bodo's merits in 1927, the unit of telegraphy speed - baud was named after him), the Italian physicist G. Caselli (in 1856 he proposed a method of photographic telegraphy and implemented it in Russia in 1866 on the Petersburg-Moscow line). It is interesting to note that most of the creators of telegraph devices were well-rounded personalities. Thus, Pyotr Lvovich Schilling was a military engineer, orientalist and diplomat, later a member of the St. Petersburg Academy of Sciences; Samuel Morse was a professor of painting at New York University in 1837. In 1866, work was completed on laying the first cable across the Atlantic Ocean. Subsequently, all continents were connected by several submarine communication lines, including fiber-optic cable.

In 1876, the American inventor A.G. Bell received a patent for the first practically usable telephone set, and in 1878 in New Haven

(USA) the first telephone exchange was introduced. In Russia, the first city telephone exchanges appeared in 1882 in St. Petersburg, Moscow, Odessa and Riga. An automatic telephone exchange (PBX) with a stepper finder introduced into

1896 (Augusta, USA.). In the 1940s. Coordinate automatic telephone exchanges were created, in the 1960s - quasi-electronic, and in the 1970s the first samples of electronic automatic telephone exchanges appeared. The development of telecommunications proceeded in parallel in many areas: telegraphy, telephony, wire sound broadcasting, radio broadcasting, radio communications, facsimile communications, television, data transmission, cellular radio communications, personal satellite communications, etc.

During 1906 - 1916. various vacuum electronic tubes were invented (Lee de Forest - USA, R. Lieben - Germany, V.I. damped oscillations), amplifiers, modulators and other devices, without which no transmission system can do.

Amplifiers of electrical signals made it possible to increase the range of wire telephone communication through the use of intermediate amplifiers, and the development of high-quality electrical filters paved the way for the creation of multichannel transmission systems with frequency division multiplexing.

The development of telephony has contributed to the introduction of wired sound broadcasting, in which sound programs are transmitted over separate wires from telephone wires. Single-program wire broadcasting was first started in Moscow in 1925 with the introduction of a 40-watt unit serving 50 loudspeakers installed in the streets. Since 1962, 3-program wire broadcasting has been introduced, in which two additional programs are transmitted simultaneously with the first method of amplitude modulation of carriers at frequencies of 78 and 120 kHz. In a number of countries, additional sound programs are broadcast over telephone networks.

The theoretical and experimental studies of many scientists, first of all M. Faraday, D. Maxwell and G. Hertz, who created the theory of electromagnetic oscillations, were the basis for the widespread use of electromagnetic waves, including the creation of wireless, i.e. radio transmission systems. An important step in the history of telecommunications was the invention of radio by A. Popov in 1895 and the wireless telegraph by G. Marconi in 1896–97. The world's first semantic radiogram, dedicated on March 12, 1896 to A.S. Popov, contained only two words "Heinrich Hertz", as a tribute to the memory of the great scientist who opened the door to the world of radio. Since that time, the use of electromagnetic waves of higher and higher frequencies began to transmit messages. This served as an impetus for the organization of radio broadcasting and the appearance of broadcasting receivers - the first household radio-electronic devices. The first broadcasts began in 1919–20. from the Nizhny Novgorod radio laboratory and from experimental broadcasting stations in Moscow, Kazan and other cities. To the same

the beginning of regular broadcasting in the USA (1920)

v Pittsburgh and Western Europe (in 1922) in London.

V In our country, regular radio broadcasting began more than 65 years ago and is now carried out on long, medium and short waves by the method of amplitude modulation, as well as in the VHF range (meter waves) by the method of frequency modulation. Stereo programs are transmitted in the VHF range. The development of radio broadcasting follows the path of introducing digital technologies in all areas of program preparation, transmission, recording and reception. A number of countries have introduced digital broadcasting systems based on DRM and DAB standards.

In 1935, between New York and Philadelphia (distance 150 km), a radio link was built for 5 telephone channels, operating in the meter wave range, steadily propagating within the line of sight. It was a chain of transmitting and receiving radio stations (two terminal and two (after 50 km) intermediate - relay) separated from each other at a distance of direct visibility of their antennas. So it appeared the new kind radio communications - radio relay communications, in which they later switched to the ranges of decimeter and centimeter waves. A distinctive feature of radio relay transmission systems is the ability to simultaneously operate a huge number of such systems in the same frequency range without mutual interference, which is explained by the possibility of using highly directional antennas (with a narrow radiation pattern).

To increase the distance between the stations, their antennas are installed on masts or towers with a height of 70-100 m and, if possible, on elevated places. In these ranges, it is possible to transmit large amounts of information, besides, the level of atmospheric and industrial interference is low here. Radio relay systems are quickly deployed (built), provide greater savings in non-ferrous metals compared to cable (coaxial) lines. Despite strong competition from fiber-optic and satellite systems, radio relay systems are indispensable in many cases - for transmitting any message (usually television images) from a mobile vehicle to a receiving station with a narrow beam of radio waves. Modern radio relay systems are mostly digital.

V 1947 the first message about a digital transmission system with pulse-code modulation (PCM) developed by Bell (USA). Since it was made on lamps (transistors did not exist yet), it was very cumbersome, consumed a lot of electricity and had low reliability. Only in 1962 a digital multichannel telecommunications system (MSTK) with time division of channels (PCM-24) was put into operation. Today, digital SITC and corresponding networks are built on the basis of a synchronous digital SDH - SDH hierarchy (with a base rate of 155.52 Mbit / s - STM-1, all other STM-n, which make up the basis of SDH equipment, provide information exchange at multiples of the base rate) and on fiber optic cable.

In 1877-80. M. Senlec (France), A. de Paiva (Portugal) and P.I.Bakhmetyev (Russia) proposed the first projects of mechanical

television. The discovery of television was facilitated by the discoveries of many scientists and researchers: A.G. Stoletov established in 1888-90. basic laws of the photoelectric effect; K. Brown (Germany) invented the cathode-ray tube in 1897; Lee de Forest (USA) created a three-electrode lamp in 1906; J. Byrd (England), C. F. Jenkins (USA), and L. S. Theremin (USSR) also made significant contributions. sweep during 1925-26. The beginning of TV broadcasting in the country on a mechanical television system with a Nipkov disc (30 lines and 12.5 frames / s) is considered to be 1931. Due to the narrow frequency band occupied by the signal of this system, it was transmitted using radio broadcasting stations in the long and medium wave ranges ... The first experiments on the electronic television system were carried out in 1911 by the Russian scientist B. L. Rosing. A significant contribution to the formation of electronic television was also made by: A. A. Chernyshev, C. F. Jenkins. A. P. Konstantinov, S. I. Kataev, V. K Zvorykin, P. V. Shmakov, P. V. Timofeev and G. V. Braude, who proposed original designs for various transmitting tubes. This made it possible to create the country's first television centers in 1937 - in Leningrad (for 240 lines) and Moscow (for 343 lines, and since 1941 - for 441 lines). Since 1948, broadcasting began on the electronic television system with decomposition into 625 lines and 50 fields / s, that is, according to the standard that is now adopted by most countries of the world (in the United States in 1940 the standard was adopted for 525 lines and 60 fields / with).

The work of many scientists and inventors on the transmission of color images (A.A. Polumordvinov proposed in 1899 the first project of a color TV system, I.A.Adamian in 1926 - a three-color sequential system) were the basis for the creation of various color television systems. The researchers and developers of the color television (DTV) system for broadcasting were faced with a difficult task: to create a system that would be mutually compatible with the already existing black and white TV system. For this, the DTV signal must be received by black-and-white televisions in black and white, and the black-and-white TV signal - by color televisions also in black and white. It took many years to successfully solve this problem. At the end of 1953, broadcasting on the NTSC DTV system (named after the national TV Systems Committee that developed it) began in the United States. In this system, a complete color TV signal is generated as the sum of the luminance and chrominance signal. The latter is a color subcarrier modulated with two color-difference signals by the method of quadrature modulation. The very method of transmitting any two messages on one subcarrier (with a phase shift of 90 °) was proposed in the 40s of the XX century by the Soviet scientist G. Momot.

However, despite the engineering simplicity of constructing encoding and decoding devices, the NTSC system has not become widespread due to the stringent requirements for the characteristics of equipment and communication channels. It took 14 years to develop other DTV systems (PAL and SECAM) that are less sensitive

to distortion of signals in the transmission channel. PAL was proposed in Germany and SECAM in France. The SECAM standard adopted for broadcasting purposes was finalized by the joint efforts of Soviet and French scientists. DTV systems NTSC, PAL and SECAM are called composite (from composite - composite, complex signal) in contrast to component systems, in which the luminance and color-difference (components) signals are transmitted separately.

V at present, TV broadcasting in the world is carried out on the three indicated analog systems in the allocated sections of meter and decimeter waves; in this case, the image is transmitted by the method of amplitude modulation of the carrier, and the soundtrack is transmitted by the method of frequency modulation of another carrier (only one standard (L) uses amplitude modulation). Analog broadcasting is gradually being replaced by digital. Number of digital TV programs by standard DVB-S, which can be received from satellites, has significantly surpassed the number of analog ones. Thousands of artificial earth satellites are launched into various space orbits, with the help of which: multi-program direct TV

– and radio broadcasting, radio communication, location (coordinates) of objects, distress alert, personal satellite communication and many other functions.

V Since 1998, the USA has begun the transition to digital high-definition television (HDTV) according to the ATSC standard (18 options are allowed, differing in the number of lines of decomposition - from 525 to 1125, the type of scan and the frequency of fields (frames)). In Europe, there is no such categorization in the transition to digital HDTV, since it is believed that the potential of the 625 line standard has not yet been fully exhausted. Nevertheless, HDTV equipment (1250 lines) is produced (especially for filming) and separate broadcasts are conducted.

To deliver TV programs to the population, radio systems are used: terrestrial in the MW and UHF ranges, satellite direct reception, microwave cellular (MMDS, LMDS, MVDS), as well as cable TV systems (coaxial, fiber-optic, hybrid). KTV systems are gaining more and more weight (from Internet access, ordering TV programs and receiving other services).

An experimental black-and-white and color stereo television system was created in the 1960s - 1970s. collective under the leadership of P. V. Shmakov in Leningrad. The introduction of stereo television into broadcasting is mainly constrained by the lack of an effective, relatively cheap and simple display device (screen). The words of P.V. Shmakov's proposal to use aircraft for retransmission of TV programs over large areas has become widespread in satellite radio communication and TV broadcasting systems. The beginning was laid

v 1965 when an artificial earth satellite (AES) was launched in the USSR"Lightning-1" with transceiver relay equipment. Today, in different orbits around the Earth, several thousand satellites revolve, having

various purposes. For direct reception of TV programs from a satellite, the optimal is a geostationary orbit, rotating along which the satellite appears to be stationary relative to any point on the Earth within the limits of radio visibility. With their help, not only TV programs are retransmitted (several hundred over European countries), but also sound broadcasting programs, personal radio communication and broadband Internet access, as well as a number of other functions.

Outstanding discovery of the 20th century. is the creation of the transistor in 1948 by W. Shockley, W. Brattain and J. Bardeen, who received Nobel Prize 1956 The success of semiconductor electronics and, in particular, the emergence of integrated circuits predetermined the rapid development of all technical means of transmitting messages by electrical means and the corresponding devices for receiving and recording them. In addition to stationary radios and televisions, portable and automobile and even personal "pocket" video equipment appeared.

The works of Soviet scientists N.G. Basova, A.M. Prokhorov and the American scientist C. Townes, who also received the Nobel Prize, made it possible in 1960 to create a laser - a highly efficient source of optical radiation. Fiber optic transmission systems (FOTS) using semiconductor laser diodes and fiber optics have become a reality since 1970, when ultrapure glass was produced in the USA. FOTS ushered in a new era in guidance technology. Due to their insensitivity to electromagnetic interference, stealth, low attenuation of transmitted optical signals (less than 0.01 dB / km), high bandwidth (more than 40 Gbit / s), they have no competitors among existing physical transmission lines. Exceptions are feeder lines (coaxial cable or waveguide), which are used to supply modulated high-frequency oscillations to radio transmitting stations. Photonic networks are being built, i.e. all optical, as well as passive, which do not contain electrical or optical amplifiers.

V a sufficiently developed backbone network has been created in our country for the transmission of any types of information via fiber-optic communication lines with access to international lines.

V In 1956, the first professional video recorder (VM) was created for recording color TV images on a magnetic tape (USA, "Ampex" company, headed by a native of Russia), its weight was 1.5 tons. Today, a camcorder (TV transmitting camera with built-in video recorder) with advanced functions fits in the palm of your hand. Since 1969, the development of household magnetic video recording began, as well as the production of small-sized studio VCRs, and then video cameras. Great demand for VM has caused competition among manufacturers (mainly from Japan).

V In the beginning, VMs of analog formats were produced: U-matic, VCR (1970); Betamax, VCR-LR, VHS (1975); Betacam, Video-2000 (1979); S-VHS (1981

g.), Video-8 (1988). But already in 1986 the first format (D-1) of digital video recording on magnetic tape of DTV signals appeared, and then D-2 (1987), D-3

(1990) and D-5 (1993). These VMs were designed to record digital streams without compression at speeds of 225, 127, 125 and 300 Mbit / s, respectively: D-1 and D-5 - component signals, D-2 and D-3 - composite signals. The successful implementation of compression algorithms - eliminating redundancy in TV images (MPEG family of standards), which significantly reduced the bit rate of the digital stream, the use of noise-immune coding methods and spectrally efficient multi-position modulation methods have opened the way for the implementation of digital TV broadcasting: an opportunity has appeared in a standard TV radio channel (8 MHz wide) for the domestic standard and most others), instead of one analogue, transmit 5 - 6 digital TV programs with stereophonic soundtrack and additional information. This was taken into account in the development of new formats for digital recording on magnetic tape as standard definition component signals.

(Betacam SX, Digital Betacam, D-7 (DVSPRO), DVSPRO50, D-9 (Digitals), DVCAM, MPEG IMX, etc.) and high (D5-HD, D-6, CAM-HD, DVSPROHD and etc.). The creators of most of the formats are Japanese companies, as well as the developers of three standards for recording digital audio signals on magnetic tape R-DAT (1981), S-DAT (1982) and an erasable disk - E-DAT (1984).

In 1977, Philips and Sony jointly developed a digital version of the disc - a compact disc for playback on a laser player. Since about 1985, the production of DVD-discs (single-layer, double-layer, single-sided and double-sided, rewritable and rewritable) and related equipment began. Portable TV cameras with an optical DVD recorder appeared. The era of tapeless preparation and production of TV programs began with information storage on disk drives, video servers with widespread use of software-controlled complexes.

Modern society cannot be imagined not only without telecommunications, but also without personal computers, local, corporate data transmission networks and the global Internet. All types of telecommunications and computer technologies have been integrated. Digital networks and systems are programmatically controlled and synchronized; digital signals are more often processed using microprocessors, signaling processes and are formed by software (for example, COFDM - the method of modulation and frequency division of several thousand orthogonal carriers is implemented in software, since it is difficult to implement hardware, and it is widely used in many digital radio transmission systems).

It all started with the simplest devices that helped a person to carry out certain calculations (accounts, adding machine, calculator). The first electronic computers were created to solve computational problems with a large amount of computation.

Under the law of the US Department of Defense from 1942 to 1946. at the University of Pennsylvania, the ENIAC (Electronic Numerical

Integrator and Automatic Calculator - electronic computational integrator and automatic calculator), which was used in the ballistic laboratory. The equipment was located in many cabinets, occupied a large room (~ 80m2), was striking in its size and weight (30 tons, 18 thousand vacuum tubes), extremely low productivity (10 - 20 thousand operations per second) - it took 3 milliseconds to multiply two numbers. This is hard for a laptop owner to believe. The MESM computer, created in 1946-1947, belongs to the first generation. in USSR.

The second generation (1960 - 1969) was developed using semiconductor devices (IBM - 701, USA; BESM-4, BESM-6, USSR). The performance increased to 100-500 thousand op / s, but the dimensions were even larger. The third generation of computers (IBM - 360, USA; EC-1030, EC-1060,

USSR) were created in 1970-1979. on microcircuits with a low degree of integration using operating systems and time-sharing. The main purpose is automated control systems, scientific and technical tasks, computer-aided design systems. Computers of the fourth generation (1980 - 1989) were built on large integrated circuits and microprocessors with a speed of tens and hundreds of mil.op / s (ILLIAC4, CRAY, USA; Elbrus, PS-2000, USSR, etc.). The scope of their application also expanded - complex production and social tasks, management, automated workstations, communications.

Simultaneously with the creation of large computers, the class of microcomputers, personal computers (PCs), developed intensively. The first microcomputer appeared in 1971 in the USA on the basis of a 4-bit microprocessor, which made it possible to drastically reduce the mass and dimensions of computing devices. As with mainframes, the first generation personal computers were hardware and software incompatible. With the advent of the IBM PC in 1981, the situation began to change towards the creation of compatible PCs with significantly higher bit depth and computational accuracy. The huge demand for high-speed PCs with advanced functionality has been the impetus for improving microprocessors, which increased from 4 in 1971 to 32 in 1986, and the clock frequency from 0.5 to 25 MHz. Modern processors are 64-bit at over 4 GHz.

The development of radio communications followed the path of mastering the ranges of ever higher frequencies, in which a much larger amount of information can be transmitted. There were many unsolved problems in the effective compression of transmitted signals, noise-immune coding and the creation of spectrally efficient digital modulation methods, and the coverage of large areas with multi-program broadcasting. The task of providing two-way radio communication with a subscriber who is on the road or does not have access to the public telephone network was also unresolved. Departmental systems of professional mobile radiotelephone communication (for ambulance, traffic and air traffic control, etc.) were created back in the 70s of the XX century (domestic systems "Altai", "Len",

"Viliya" and others). They were portable transmitting and receiving radio stations and therefore were not designed for mass use. This required making them portable and lightweight, as well as finding ways to reuse the same frequencies by different subscribers in conditions of a limited frequency resource.

The first to appear were one-way radio communication systems - paging systems (personal radio calls). They allow you to send short text messages to anyone with a portable pager receiver. The display of the received alphanumeric characters is carried out on a small screen (indicator) of the receiver. The text of such messages with the indication of the subscriber's number was first transmitted over the telephone line to the base station, and from there the operator transmitted it to the recipient's pager. This was a great achievement at the time. In the future, it became possible not only to receive messages, but also to respond to them with several standard phrases hardwired into the pager's memory.

This is how cellular mobile radio communication systems were born, the main principle of which is cellular construction and frequency distribution. The service area is divided into a large number of small cells ("cells" - hexagons) with a radius of R from 1.5 to 3 km, served by a separate low-power radio base station. A set of, for example, seven cells forms a cluster with the corresponding numbers of the frequencies used. In adjacent clusters, the same frequencies are used, but assigned to cells so that the distance between the centers of cells (different clusters) with the same frequencies is 4.5R - sufficient to exclude mutual influence.

The first SPRs were analog, then everywhere - digital. Their functionality was gradually expanded - from two-way transmission of only speech to data transmission, still and moving images (so far of average quality). The service area also increased - from a small area of ​​the city to the state as a whole, and in the presence of international agreements - on the territory of other countries. By the end of 1996 (10 years ago), the number of DSS subscribers in the world was just over 15 million.Today, there are more than 4 million subscribers in our country alone, and there are more than 2 billion of them in the world.

Another achievement of the late 20th century should be noted - the creation of the xDSL (Digital Subscribez Line) family of standards, designed to significantly increase the throughput of twisted copper pair used on the subscriber section to the PBX (hence the name "last mile"). The use of new types of multi-position modulation allows transmitting large amounts of information over a narrow-band copper pair: in the ADSL version - from the subscriber to the automatic telephone exchange - at a speed of 16 - 640 kbps, to the subscriber - 6 Mbps at a distance of 2.7 km, and in the VDSL - transmission at a speed of 52 Mbit / s (PBX - subscriber) is provided for a distance of up to 300 m. Not so long ago it was believed that such a channel could not transmit a TV signal at all. Thus, with

VDSL technology can transmit up to 10 digital TV programs (5 Mbps per program) of broadcast quality, which is a colossal achievement.

The history of the development of communication lines in Russia The first long-distance overhead line was built between St. Petersburg and Warsaw in 1854. In the 1870s, an overhead communication line from St. Petersburg to Vladivostok L = 10 thousand km was put into operation. In 1939, a high-frequency communication line from Moscow to Khabarovsk L = 8,300 thousand km was put into operation. In 1851 a telegraph cable was laid from Moscow to St. Petersburg, insulated with gutta-percha tape. In 1852, the first submarine cable was laid across the Northern Dvina.In 1866, a cable transatlantic telegraph communication line between France and the United States was put into operation

The history of the development of communication lines in Russia In the years in Russia, the first aerial urban telephone networks were built (the cable consisted of up to 54 cores with air-paper insulation) In 1901, the construction of an underground city telephone network began in Russia. winding to artificially increase the inductance. Since 1917, a telephone amplifier on electronic tubes was developed and tested on the line, in 1923 a telephone connection with amplifiers was carried out on the Kharkov-Moscow-Petrograd line. From the beginning of the 30s, multichannel transmission systems based on coaxial cables began to develop.

The history of the development of communication lines in Russia In 1936 the first coaxial HF telephone line for 240 channels was put into operation. In 1956, an underwater coaxial telephone and telegraph trunk line between Europe and America was built. In 1965, the first experimental waveguide lines and cryogenic cable lines with very low attenuation appeared. By the early 1980s, fiber-optic communication systems were developed and tested in real conditions.

Types of communication lines (LANs) and their properties There are two main types of LANs: - lines in the atmosphere (radio lines RL) - directing transmission lines (communication lines). typical wavelength and radio frequency ranges Ultra-long waves (VLW) Long waves (LW) Medium waves (MW) Short waves (HF) Ultra-short waves (VHF) Decimeter waves (DCM) Microwave(CM) Millimeter waves (MM) Optical range km (kHz) km (kHz) 1.0 ... 0.1 km (0, MHz) m (MHz) m (MHz), 1 m (0, GHz) cm (GHz) mm (GHz), 1 μm

The main disadvantages of RL (radio communication) are: -dependence of the quality of communication on the state of the transmission medium and third-party electromagnetic fields; -low speed; insufficiently high electromagnetic compatibility in the range of meter waves and above; - the complexity of the transmitter and receiver equipment; - narrowband transmission systems, especially at long waves and above.

In order to reduce the disadvantages of radar, higher frequencies (centimeter, optical ranges) decimeter millimeter range are used. This is a chain of repeaters installed every 50 km-100 km. RRL allows you to receive the number of channels () over distances (up to km); These lines are less susceptible to interference, provide a fairly stable and high-quality connection, but the degree of transmission security over them is insufficient. Radio relay lines (RRL)

Centimeter wavelength range. SLs allow multichannel communication at an "infinite" distance; Satellite communication lines (SL) Advantages of SL - a large coverage area and transmission of information over long distances. The disadvantage of SL is the high cost of launching a satellite and the complexity of organizing duplex telephone communication.

Advantages of directing LANs - high quality of signal transmission, - high transmission speed, - great protection from the influence of third-party fields, - relative simplicity of terminal devices. Disadvantages of directing drugs - high cost of capital and operating costs, - the relative duration of establishing a connection.

Radar and LS do not oppose, but complement each other. At present, signals from direct current to the optical frequency range are transmitted via communication lines, and the operating wavelength range extends from 0.85 microns to hundreds of kilometers. - cable (CL) - air (VL) - fiber-optic (FOCL). The main types of targeted drugs:

BASIC REQUIREMENTS FOR COMMUNICATION LINES - communication over distances up to km within the country and up to international communication; - broadband and suitability for the transmission of various types of modern information (television, telephony, data transmission, broadcasting, transmission of newspaper strips, etc.); -protection of circuits from mutual and external interference, as well as from thunderstorms and corrosion; - stability of electrical parameters of the line, stability and reliability of communication; - the efficiency of the communication system as a whole.

Modern development cable technology 1. The predominant development of coaxial systems that allow organizing powerful communication beams and transmission of television programs over long distances via a single-cable communication system. 2. Creation and implementation of promising communication channels that provide a large number of channels and do not require scarce metals (copper, lead) for their production. 3. Widespread introduction of plastics (polyethylene, polystyrene, polypropylene, etc.) into cable technology, which have good electrical and mechanical characteristics and allow you to automate production.

4. Introduction of aluminum, steel and plastic casings instead of lead ones. The sheaths must be airtight and ensure the stability of the electrical parameters of the cable during the entire service life. 5. Development and introduction into production of cost-effective designs of intra-zone communication cables (single-coaxial, single-quadrant, unarmored). 6. Creation of shielded cables that reliably protect the information transmitted through them from external electromagnetic influences and thunderstorms, in particular, cables in two-layer sheaths such as aluminum steel and aluminum lead.

7. Increasing the dielectric strength of the insulation of communication cables. A modern cable must simultaneously possess the properties of both a high-frequency cable and a power electric cable, and ensure the transmission of high voltage currents for remote power supply of unattended amplifying points over long distances.

The central office of the company is located in the capital of Kazakhstan - the city of Astana. The company employs about 30 thousand people. Kazakhtelecom JSC has regional divisions in each region of the country and provides communication services throughout the country.

Introduction. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .3
Chapter 1. General characteristics of the enterprise. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .4
1.Historical reference. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 4
2. Organizational structure of the enterprise. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 5
3. Organization of the production process. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 7
4. Basic economic and financial indicators. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... eight
Chapter 2. Marketing research of OJSC Rostelecom. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 12
Chapter 3 Conclusions and Suggestions for the Entire Body of the Report. ... ... ... ... ... ... ... ... ... ... ... ... ... .17
Conclusion. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .twenty
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1. The history of the development of communication lines

Communication lines arose simultaneously with the advent of the electric telegraph. The first communication lines were cable. However, due to the imperfect design of cables, underground cable communication lines soon gave way to overhead ones. The first long-distance air line was built in 1854 between St. Petersburg and Warsaw. In the early 70s of the last century, an overhead telegraph line was built from St. Petersburg to Vladivostok with a length of about 10 thousand km. In 1939, the world's longest high-frequency telephone trunk line Moscow-Khabarovsk with a length of 8300 km was put into operation.

The creation of the first cable lines is associated with the name of the Russian scientist P.L. Schilling. Back in 1812, Schilling in St. Petersburg demonstrated the explosions of sea mines, using for this purpose an insulated conductor he had created.

In 1851, simultaneously with the construction of the railway between Moscow and St. Petersburg, a telegraph cable was laid, insulated with gutta-percha. The first submarine cables were laid in 1852 through the Northern Dvina and in 1879 across the Caspian Sea between Baku and Krasnovodsk. In 1866, a cable transatlantic telegraph trunk line between France and the United States was put into operation.

In 1882-1884. the first urban telephone networks in Russia were built in Moscow, Petrograd, Riga, Odessa. In the 90s of the last century, the first cables with up to 54 cores were suspended on the city telephone networks of Moscow and Petrograd. In 1901, the construction of the underground city telephone network began.

The first designs of communication cables, dating back to the beginning of the 20th century, made it possible to carry out telephone transmission over short distances. These were the so-called city telephone cables with air-paper insulation of cores and twisting them in pairs. In 1900-1902. was

a successful attempt was made to increase the transmission distance by artificially increasing the inductance of cables by including inductance coils into the circuit (Pupin's proposal), as well as using conductive cores with a ferromagnetic winding (Krarup's proposal). Such methods at that stage made it possible to increase the range of telegraph and telephone communications several times.

An important stage in the development of communication technology was the invention, and since 1912-1913. mastering the production of electronic tubes. In 1917 V.I. Kovalenkov developed and tested on the line a telephone amplifier based on electronic tubes. In 1923, telephone communication with amplifiers was established on the Kharkov-Moscow-Petrograd line.

The development of multichannel transmission systems began in the 1930s. Subsequently, the desire to expand the spectrum of transmitted frequencies and increase the capacity of lines led to the creation of new types of cables, the so-called coaxial. But their mass production refers only to 1935, at the time of the appearance of new high-quality dielectrics such as escapon, high-frequency ceramics, polystyrene, styroflex, etc. These cables are capable of transmitting power at currents of up to several million hertz and enable the transmission of television programs over long distances. The first coaxial line for 240 HF telephony channels was laid in 1936. The first transatlantic submarine cables, laid in 1856, were used only for telegraph communication, and only 100 years later, in 1956, an underwater coaxial trunk line was built between Europe and America for multichannel telephony.

In 1965-1967. experimental waveguide communication lines for the transmission of broadband information appeared, as well as cryogenic superconducting cable lines with very low attenuation. Since 1970, work has been actively developed to create light guides and optical cables using visible and infrared radiation in the optical wavelength range.

The development of an optical fiber and the production of cw generation of a semiconductor laser played a decisive role in the rapid development of fiber-optic communication. By the early 1980s, fiber-optic communication systems had been developed and tested in real conditions. The main areas of application of such systems are the telephone network, cable television, intra-object communications, computer technology, monitoring and control systems for technological processes, etc.

Urban and intercity fiber-optic communication lines have been laid in Russia and other countries. They are assigned a leading place in the scientific and technological progress of the communications industry.

2. Design and characteristics of optical communication cables

Varieties of optical communication cables

An optical cable consists of silica glass optical fibers (optical fibers) twisted in a certain system, enclosed in a common protective sheath. If necessary, the cable can contain power (reinforcing) and damping elements.

Existing OK, according to their purpose, can be classified into three groups: trunk, zonal and urban. Underwater, object and assembly OKs are allocated into separate groups.

Trunk OK are intended to transmit information over long distances and a significant number of channels. They must have low attenuation and dispersion and high data throughput. A single-mode fiber with core and cladding dimensions 8/125 microns is used. Wavelength 1.3 ... 1.55 μm.

Zonal OKs are used to organize multi-channel communication between the regional center and districts with a communication range of up to 250 km. Gradient fibers with a size of 50/125 microns are used. Wavelength 1.3 μm.

Urban OK are used as connecting lines between city automatic telephone exchanges and communication centers. They are designed for short distances (up to | 10 km) and a large number of channels. Gradient fibers (50/125 microns). Wavelengths 0.85 and 1.3 μm. These lines generally operate without intermediate line regenerators.

Underwater OCs are designed to communicate across large water obstacles. They must have high mechanical tensile strength and have reliable moisture resistant coatings. It is also important for subsea communications to have low attenuation and long regeneration lengths.

Object OK are used to transfer information within an object. This includes office and video telephone communications, an internal cable television network, as well as on-board information systems of mobile objects (aircraft, ships, etc.).

Mounting OK are used for intra- and inter-unit installation of equipment. They are made in the form of bundles or flat strips.

Optical fibers and features of their manufacture

The main element of the OC is an optical fiber (light guide) made in the form of a thin glass fiber of a cylindrical shape, through which light signals with wavelengths of 0.85 ... 1.6 μm are transmitted, which corresponds to the frequency range (2.3 ... 1 , 2) 1014 Hz.

The light guide has a two-layer structure and consists of a core and a cladding with different refractive indices. The core is used to transmit electromagnetic energy. The purpose of the cladding is to create better reflection conditions at the core-cladding interface and to protect against interference from the surrounding space.

The core of the fiber, as a rule, consists of silica, and the cladding can be silica or polymer. The first fiber is called quartz-quartz, and the second is quartz-polymer (silicon-organic compound). Based on the physical and optical characteristics, preference is given to the first one. Quartz glass has the following properties: refractive index 1.46, thermal conductivity coefficient 1.4 W / mk, density 2203 kg / m3.

Outside the fiber is a protective coating to protect it from mechanical stress and color application. The protective coating is usually made in two layers: first, an organosilicon compound (SIEL), and then epoxydrylate, fluoroplastic, nylon, polyethylene or varnish. Total fiber diameter 500 ... 800 μm

Three types of optical fibers are used in the existing optical fiber structures: stepped with a core diameter of 50 μm, gradient with a complex (parabolic) profile of the refractive index of the core, and single-mode with a thin core (6 ... 8 μm)

In terms of frequency bandwidth and transmission range, single-mode fibers are the best, and stepped ones are the worst.

The most important problem of optical communication is the creation of optical fibers (OF) with low losses. Quartz glass is used as a starting material for the production of optical fiber, which is a good medium for the propagation of light energy. However, as a rule, glass contains a large amount of foreign impurities such as metals (iron, cobalt, nickel, copper) and hydroxyl groups (OH). These impurities lead to a significant increase in losses due to absorption and scattering of light. To obtain an optical fiber with low losses and attenuation, it is necessary to get rid of impurities so that the glass is chemically pure.

At present, the most widespread method of creating an OM with low losses by chemical vapor deposition.

The production of OM by chemical vapor deposition is carried out in two stages: a two-layer quartz preform is made and a fiber is drawn from it. The workpiece is manufactured as follows

A jet of chlorinated quartz and oxygen is fed into a hollow quartz tube with a refractive index 0.5 ... 2 m long and 16 ... 18 mm in diameter. As a result of a chemical reaction at a high temperature (1500 ... 1700 ° C), pure quartz is deposited in layers on the inner surface of the tube. Thus, the entire inner cavity of the tube is filled, except for the very center. To eliminate this air channel, an even higher temperature (1900 ° C) is applied, due to which collapse occurs and the tubular billet turns into a solid cylindrical billet. Pure deposited quartz then becomes the core of the OF with a refractive index, and the tube itself acts as a cladding with a refractive index. Fiber extraction from the workpiece and its winding on the receiving drum are carried out at the glass softening temperature (1800 ... 2200 ° C). More than 1 km of optical fiber is obtained from a 1 m long workpiece.

The advantage of this method is not only the production of an optical fiber with a core of chemically pure quartz, but also the possibility of creating gradient fibers with a given refractive index profile. This is done: through the use of doped quartz with an addition of titanium, germanium, boron, phosphorus or other reagents. The refractive index of the fiber can vary depending on the additive used. So, germanium increases and boron decreases the refractive index. By selecting the formulation of doped quartz and observing a certain amount of additive in the layers deposited on the inner surface of the tube, it is possible to provide the required character of change over the cross section of the fiber core.

Optical cable designs

OK designs are mainly determined by the purpose and scope of their application. In this regard, there are many design options. A large number of cable types are currently being developed and manufactured in various countries.

However, all the variety of existing types of cables can be divided into three groups

concentric twisted cables

shaped core cables

flat ribbon cables.

The cables of the first group have a traditional concentric twisting of the core by analogy with electric cables. Each subsequent twist of the core has six more fibers than the previous one. Such cables are known mainly with the number of fibers 7, 12, 19. Most often, the fibers are located in separate plastic tubes, forming modules.

The cables of the second group have a shaped plastic core with grooves in the center, in which the optical fiber is placed. The grooves and, accordingly, the fibers are located along the helicoid, and therefore they do not experience longitudinal tensile stress. These cables can contain 4, 6, 8 and 10 fibers. If it is necessary to have a large cable capacity, then several primary modules are used.

A ribbon cable consists of a stack of flat plastic strips, into which a certain number of optical fibers are mounted. Most often, a tape contains 12 fibers, and the number of tapes is 6, 8 and 12. With 12 tapes, such a cable can contain 144 fibers.

In addition to optical fiber, optical cables usually have the following elements:

power (hardening) rods, taking on a longitudinal load, to break;

fillers in the form of continuous plastic filaments;

reinforcing elements that increase the durability of the cable under mechanical stress;

outer protective sheaths that protect the cable from moisture, vapors of harmful substances and external mechanical influences.

Various types and designs of OK are manufactured in Russia. For the organization of multichannel communication, mainly four- and eight-fiber cables are used.

French-made OKs are of interest. They, as a rule, are completed from unified modules consisting of a plastic rod 4 mm in diameter with ribs along the perimeter and ten OVs located along the periphery of this rod. The cables contain 1, 4, 7 of these modules. Outside, the cables have an aluminum and then a polyethylene sheath.

Prospects for the development of cable communication lines in the third millennium

Prospects for the development of cable communication lines in the third millennium are considered. It is shown that the main direction of the development of networks is the replacement of cables with copper conductors with optical communication cables in the primary network. Clothes, given the huge size of the territory of Russia, while maintaining the existing rates of introduction of optical cables, according to optimistic protoems, the complete replacement of existing copper cables with optical ones will take 60 years. , but this does not take into account the development of modern transport and technological infrastructure. By 2030, the transport telecommunications infrastructure can be replaced, and by 2069 the replacement of the entire existing infrastructure with an opp + yu cable

Portnov EL.,

The basic principles of creating telecommunication networks in the third millennium is the creation of a single network based on fiber-optic communication lines. At present, the transmission network of telecommunications is based on symmetric, coaxial and fiber-optic communication lines. Despite the fact that symmetrical and coaxial communication cables occupied the main place on the backbone and intra-zone primary network of all ministries and departments, all new construction in the leading ministries and departments is currently being carried out on an optunsk communication cable. In other words, the transport section of the network ( long-distance, intra-zone AND city) is subordinated to FIBER-OPTICAL technologies. The access network (urban and rural communication) is also based on a fiber-optic cable (fiber to the cable cabinet, fiber to the house, fiber to the subscriber, fiber to the desktop) during new construction.

With fiber to the cabinet, it is assumed at the modern level that a cable with copper conductors is being sought from the cabinet to the subscriber; with fiber to the house, it is assumed that the distribution and subscriber sections in the house are made by a male with copper conductors (symmetrical or coaxial); with fiber to the subscriber, it is assumed that a copper cable will go from the junction box to the device and the computer, and a coaxial radio-frequency cable will go to the TV; with fiber on the table, fiber-optic technology will be implemented, while maintaining the copper subscriber wiring and RF coaxial cable to the TV

By 2015, Russia plans to fully integrate existing networks (including mobile networks, broadcasting and the Internet) into a single federation of networks. In 2007, the Internet schedule in the world amounted to 6 Pitobytes per day, while the total speed over one optical fiber reached 4 Tbps, and over copper 1 Gbps

At present, the total record transmission rates of 14 Tbit / s have been obtained over optical fiber, while the transmission rate in one channel has been reached 1 Tbit / s; the number of channels in one fiber was 1 000 at a transmission rate of 3.25 Gbit / s However, for commercial use no more than 100 channels are used at a transmission rate of 40 Gbit / s

As the demand for telecommunications and multiservice services grows, the demand for optical fiber (and, therefore, for an optical male) is not decreasing and amounts to 70 million km. with an annual growth rate of 15%. 70 million km of optical fiber is allocated for long-distance terrestrial and submarine communication cables,

access network cables, intra-zone and urban, rural network cables, local network cables and structured cabling systems. The increase in demand for these cables is increasing, as can be judged by the demand for optical fiber:

For trunk cables

(ground and underwater) communications - 10%

For access network cables - 25%

For intra-zone cables,

urban and rural networks - 40%

For local and structured cables

cable networks - 5%

Undoubtedly, the priority direction is the direction of the wide development of fiber-optic cables at all levels of the primary network: transport and access, further development of copper cables on public networks, on access networks, cables of structured cable systems, radio frequency coaxial males for cable television networks

Of all the variety of directing telecommunication systems (Fig. 1), only optical communication males, symmetrical communication cables of the public network, symmetrical communication cables based on twisted pair and radio frequency cables for the cable television network are now widely produced by factories

It should be noted that for the digital transmission format for computer networks, twisted pair cables are widely used, which fits into the nomenclature of symmetrical communication cables based on the existing categories:

access from 100 MHz and above is limited to a length of 100 meters, therefore, they are used only on the access network in computer networks, and the transport stream is delivered via optical fiber.

The dimensions and characteristics of optical fibers used in telecommunications should be in accordance with the MRZ-T Recommendations:

P.651 (multimode gradient fibers 50/125 microns);

P.652 (single-mode fibers);

P.653 (dispersion-shifted single-mode fiber);

C.654 (single-mode fiber with attenuation minimized at 1550nm);

T-Sott, # 8-2010

INFORMATION SOCIETY TECHNOLOGIES

VOKS lpv VL EZhD

VLS - overhead communication lines, SK - symmetric communication cables, KK - coaxial kobe / i s wadi, GSK - urban symmetric communication cables, SSK * rural symmetric communication cables, ZSH - zone symmetric communication cables, MSK - trunk symmetric communication cables, MSK - mappings coaxial cables ^ e communication cables, ZSK - zone coaxial communication males, SPKK - special coaxial cables ", RKK - radio frequency cosmic cables, communication / 1SGSK - parallel networks. cables based on twisted pair, armored personnel carriers - shielded symmetrical cables based on a twisted hearth, LK - ribbon cables for communication, VOKS - fiber-optic communication cables, YP V - l "* of surface wiring, VL - high-voltage transmission, EZD - alectofified Railway, MOKS - master fiber / optical fiber cables, GKHS- submarine fiber-optic cables, ZOKS - zone fiber-optic males, GOKS - urban fiber-optic cables, SOKS - special fiber-optic cables, VVP - aerial high-voltage / transmission line, KVL - cable high-resilience transmission line, VEZhD - ground-based electrification on the railway, LOK - more sp-t ^ ekie cables, "telephone" optical cables

S-655 (single-mode fibers with shifted non-zero dispersion, including: with a small slope of the dispersion curve, with a large effective area of ​​the bridging field);

<3-656 (одномодовое широкополосное оптическое волокно с ненулевой смещенной д исперсией до 1625 нм);

С-657 (single-mode optical fiber with a minimum bending radius).

The classification of optical cables depending on the types of use is shown in Fig. 2-6.

When designing fiber-optic cables, protection of the fiber from additional attenuation and excessive mechanical deformation under various operating conditions must be provided, and changes in the geometric dimensions of the cable that affect the workers must be taken into account. fiber characteristics. In addition, the fiber must be such that it is easy to run and splicate the fibers in the cable glands, or join on the posts when terminating cables.

Russia is the largest country in terms of territory: it occupies 12.8% of the earth's land, and lives on this territory only 2.4% of the total population of the earth, that is, the population density is only 9. Therefore, to provide the settlement with communication means and services it is required to build very long communication lines at high capital costs for their creation.

Russia's harsh climate and demographic and economic heterogeneity exacerbate Russia's difficulties in developing communications in general.

Since the beginning of the 90s of the last century, the construction of new communication lines on cables with copper conductors has ceased on the backbone and intra-zone networks of public use, however, the huge network created for decades on cables with copper conductors is 2-3 times larger than the modern network on optical communication cables ... A transport network on a copper cable cannot compete with an optical transport network in terms of bandwidth, digital signal quality, length, and a number of other characteristics.

Therefore, the primary task in the transport network is to replace cable lines with copper conductors with optical cable lines. Over a ten-year period of time, 140 thousand km of optical communication lines have been built on the backbone and intra-zone public networks and technological networks. If the pace of construction is maintained, only by 2030 will it be possible to replace cable lines with copper conductors with optical ones on the above networks. But there is still a large group of cable lines on the public access network with copper conductors, and their length is also considerable.

Line cables C Zh

Interl> jurolishs OK Distribution OK Soslingslyye OK

oists | [ok sks [

Fig 2. Classification of OK for external services

OK DM ■ FTISHYUY OK for

gaskets ok

Sun. 3. Classification OK for internal lining

Therefore, the primary task in the transport network is to replace cable lines with copper conductors with optical cable lines. Over a ten-year period of time, 140 thousand km of optical communication lines have been built on backbone and intra-zone public networks and technological networks. If the pace of construction is maintained, only by 2030 will it be possible to replace cable lines with copper conductors with optical ones on the above networks. But there is an even larger group of cable lines on the public access network with copper conductors, and their length is also considerable.

In other words, by 2030 the transport infrastructure of optical cable lines can be solved, which in length by this time will be 636 THOUSAND KM.

At the same time, the existing transport and technological infrastructure in Russia, excluding its development, is presented below:

T-Sott, # 8-2010

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