Stages of development of wire communication systems. Pages of history: The emergence and development of long-distance communications in Russia

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 was put into operation from Moscow to Khabarovsk L = 8,300 thousand km. 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 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 overhead city telephone networks were built (the cable totaled up to 54 wires 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 based on vacuum tubes has been developed and tested on the line; in 1923, telephone communication with amplifiers was carried out on the Kharkov-Moscow-Petrograd line. Since the beginning of the 1930s, 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 was put into operation telephone line for 240 channels. In 1956, an underwater coaxial telephone and telegraph trunk was built between Europe and America. In 1965, the first experimental waveguide lines and cryogenic cable lines with very little damping. By the beginning of the 1980s, fiber-optic communication systems had been developed and tested in real conditions.

Types of communication lines (LS) and their properties There are two main types of LS: - lines in the atmosphere (RL radio links) - guide transmission lines (communication lines). typical wavelengths and radio frequencies Extra long waves (VLF) Long waves (LW) Medium waves (MW) Short waves (HF) Ultrashort waves (VHF) Decimeter waves (DCM) Centimeter waves (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 communications) are: -dependence of the quality of communication on the state of the transmission medium and external electromagnetic fields; -low speed; insufficiently high electromagnetic compatibility in the range of meter waves and above; - the complexity of the transmitter and receiver equipment; - narrow-band transmission systems, especially at long wavelengths and higher.

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

Centimeter wave range. SLs allow for multi-channel communication over an “infinite” distance; Satellite communication lines (SL) Advantages of SL - a large area of coverage 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 LANs - high cost of capital and operating costs, - 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, 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 directional drugs:

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

Modern development cable technology 1. The predominant development of coaxial systems that allow organizing powerful communication bundles and transmitting television programs to long distances over a single cable communication system. 2.Creation and implementation of promising communication OKs 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 to automate production.

4. The introduction of aluminum, steel and plastic shells instead of lead. The sheaths must be airtight and ensure the stability of the electrical parameters of the cable throughout the entire service life. 5. Development and introduction into production of economical designs of cables for intrazonal communication (single-coaxial, single-quad, unarmoured). 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 electrical strength of the insulation of communication cables. A modern cable must simultaneously have the properties of both a high-frequency cable and a power electric cable, and ensure the transmission of currents high voltage for remote power supply of unattended amplifying points over long distances.

First steps towards knowledge. Stephen Gray (1670-1736)

The conductive structure consisted of a glass tube and a cork placed in it. When the tube was rubbed, the cork began to attract small pieces of paper and straw. Gradually increasing the length of the cork, putting wood chips into it, Gray noted that the same effect was valid until the end of the chain.

By replacing the cork with a wet hemp rope, he managed to reach a length of the transmitted electric charge distance of up to 250 meters.

But it was necessary to make sure that the electricity was not transmitted by gravity in a vertical position, and Gray repeated the experiment, placing the structure in a horizontal position. The experiment was doubly successful, as it was found that this is not transmitted over the earth.

Later it turned out that not all substances have the property of electrical conductivity. In the course of further research, they were divided into "conductors" and "non-conductors". As you know, the main conductors are all types of metals, solutions of electrolytes, salts, coal.

Non-conductors include substances where electric charges cannot move freely, such as gases, liquids, glass, plastic, rubber, silk and others.

Thus, Stephen Gray revealed and proved the existence of such phenomena as electrostatic induction, as well as the distribution and movement of electric charge between bodies.

For his achievements and contribution to the development of science, the scientist was not only the first nominee, but also the first to be awarded the highest award of the Royal Society - the Copley Medal.

On the way to isolation. Tiberio Cavallo (1749–1809)

A follower of Stefano Gray in the field of electrical conductivity research, Tiberio Cavallo, an Italian scientist living in England, developed a method for insulating wires in 1780.

Their proposed scheme was the following sequence of actions:

Two stretched wires made of copper and brass must be calcined either in a candle fire or with a red-hot iron piece, then covered with a layer of resin, and then a piece of resin-impregnated linen tape is wound around them.

Then it was covered with an additional protective layer "woolen cover". It was meant to manufacture such products in segments from 6 to 9 meters. To obtain a greater length, the parts were connected by winding on pieces of silk impregnated with oil.

The first cable and its application. Francisco de Salva (1751–1828)

Francisco Salva, a well-known scientist and physician in Spain, in 1795 appeared before the members of the Barcelona Academy of Sciences with a report on the telegraph and its communication lines, in which the term "cable" was first used.

He argued that the wires could not be located remotely, but on the contrary, they could be twisted in the form of a cable, which makes it possible to place it suspended in the air.

This was revealed in the course of experiments with cable insulation: all the wires contained in the composition were first wrapped with resin-impregnated paper, then they were twisted and additionally wrapped in multilayer paper. Thus, the elimination of the loss of electricity was achieved.

At the same time, Salva suggested the possibility of waterproofing, given the fact that the scientist could not know about the materials applicable for this kind of construction.

Francisco Salva developed a project for overhead transmission lines between Madrid and Aranjuez, which was carried out for the first time in 1796 in the world. Later, in 1798, a "royal" communication line was erected.

At the dawn of the formation of human society, communication between people was very scarce. A branch stuck into the ground indicated in which direction and how far the people had gone; specially placed stones warned of the appearance of enemies; notches on sticks or trees reported hunting prey, etc. There was also a primitive transmission of signals over a distance. Messages encoded as a certain number of cries or drum beats with a changing rhythm contained this or that information.

The tenth volume of the "General History" of the ancient Greek historian Polybius (c. 201-120 BC) describes a method of transmitting messages over a distance using torches (torch telegraph), invented by the Alexandrian scientists Cleoxenus and Democlitus.

In 1800, the Italian scientist A. Volta created the first chemical current source. This invention made it possible for the German scientist S. Semmering to build and present in 1809 to the Munich Academy of Sciences a project for an electrochemical telegraph. In October 1832, the first public demonstration of the electromagnetic telegraph by the Russian scientist P.L. Schilling. In the same year, with the help of Schilling's telegraph, a connection was established between the Winter Palace and the Ministry of Railways.

A real revolution in the field of telecommunications by wire was made by the Russian academician B.S. Jacobi and the American scientist S. Morse, who independently proposed a writing telegraph.

In 1841 B.S. Jacobi put into operation a line equipped with a writing telegraph and connecting Winter Palace with the Headquarters. Two years later, a similar line with a length of 25 km was built between St. Petersburg and Tsarskoye Selo. In 1850 B.S. Jacobi designed the first direct-printing machine. In June 1866, a cable was laid through Atlantic Ocean. Europe and America were connected by telegraph.

The birth of the telegraph gave impetus to the appearance of the telephone. Since 1837, many inventors have tried to transmit human speech over a distance using electricity. In 1876 American inventor A.G. Bell patented a device for transmitting voice over wires - the telephone. In 1878, the Russian scientist M. Makhalsky designed the first sensitive microphone with carbon powder.

At first, telegraph lines were used for telephone communications. A special two-wire telephone line was designed in 1895 by Professor P.D. Voinarovsky and was built in 1898 between St. Petersburg and Moscow.

In 1886, the Russian physicist P.M. Golubitsky developed a new telephone communication scheme. According to this scheme, the microphones of subscriber telephones were powered by one (central) battery located at the telephone exchange. The first telephone exchanges in Russia were built in 1882–1883. in Moscow, Petersburg, Odessa.

The first public demonstration of A.S. Popov for receiving electromagnetic waves took place on May 7, 1895. This day went down in history as the day the radio was invented.

Employees of the Nizhny Novgorod laboratory established in 1918 (it was headed by M.A. Bonch-Bruevich) already in 1922 built in Moscow the world's first broadcasting station with a capacity of 12 kW.

In 1935, between New York and Philadelphia, a radio link on ultrashort waves was put into operation, which was later called the “radio relay line”.

From now on, chains of radio relay lines stretched to all ends of the globe. The construction of the first radio relay line in our country was carried out in 1953 between Moscow and Ryazan.

“Beep...beep...beep.” These signals were heard on October 4, 1957 by the whole world. The era of space exploration has arrived. A very short time separates us from this date, and thousands of artificial satellites have already been launched into space orbits, regularly serving man.

On April 23, 1965, the Molniya-1 artificial Earth satellite was launched in the USSR, on board of which there was a transceiver and relay station.

In 1960, the world's first laser was created in America. This became possible after the appearance of the works of Soviet scientists V.A. Fabrikant, N.G. Basova and A.M. Prokhorov and the American scientist C. Towns, who received the Nobel Prize.

“Teach” lasers to transmit information over a distance began shortly after their invention. The first laser communication lines appeared in the early 60s of this century. In our country, the first such line was built in 1964 in Leningrad.

Muscovites are well acquainted with such corners of the capital as Leninskiye Gory and Zubovskaya Square. In 1966, a red thread of laser light shone between them. She connected two city exchanges located at a distance of 5 km from each other.

In 1970, ultrapure glass was produced by the American company Corning Glass Company. This made it possible to create and introduce optical communication cables everywhere.

In 1947, the first mention of a pulse code modulation (PCM) system developed by Bell appeared. The system turned out to be cumbersome and unworkable. It was only in 1962 that the first commercial transmission system IKM-24 was put into operation.

Modern trends in the development of telecommunications. In subsequent years, communications developed along the path of digitalization of all types of information. This has become the general direction, providing economical methods not only for its transmission, but also for distribution, storage and processing.

The intensive development of digital transmission systems is explained by the significant advantages of these systems in comparison with analog transmission systems: high noise immunity; weak dependence of the transmission quality on the length of the communication line; stability of electrical parameters of communication channels; efficient use of bandwidth in the transmission of discrete messages, etc.

In 2002, the development of local telephone communication was carried out mainly on the basis of modern digital exchanges, which made it possible to improve the quality and expand the range of services provided. The coefficient of capacity of digital stations from the total installed capacity of the local telephone network in 2002. amounted to about 40% against 36.2% in 2001. As of January 1, 2003, about 195,000 long-distance and local payphones operated on Russian networks, including 63,000 universal ones. The number of payphones increased by 13% and amounted to 127.5 thousand units. The increase in the number of main telephone sets in the local telephone network amounted to 1.8 million units, mainly due to telephone sets installed by the population. The total number of subscribers of cellular mobile communications in Russia at the end of 2002 amounted to 17.7 million, the increase in the subscriber base in relation to 2001 was 2.3 times. In 2002, over the year, the computer park in Russia increased by 20% compared to 2001. The number of regular Internet users increased by 39% and reached 6 million people. The volume of the domestic IT market grew by 9% and amounted to more than 4 billion rubles. dollars. In 2002, more than 50,000 km of cable and radio relay communication lines, 3 million automatic telephone exchange numbers, more than 13 million mobile telephone numbers, and over 70,000 long-distance and international channels were put into operation.

Mobile radio communication networks are developing at a particularly fast pace in the world and in our country. By the number of subscribers of the mobile communication system, one can already judge the level and quality of life in a given country. In this sense, the growth rate of mobile subscribers in Russia (almost 200% per year) is an indicator of the growth of the welfare of society.

Based macroeconomic indicators development Russian Federation, defined in the Guidelines for the long-term socio-economic policy of the Government of the Russian Federation, the telecommunications services market by 2010 will be characterized as follows (Table 1).

Table 1. Indicators of the development of telecommunications in Russia for the period up to 2010

Mankind is moving towards the creation of the Global Information Society. Its basis will be the Global Information Infrastructure, which will include powerful transport communication networks and distributed access networks that provide information to users. Globalization of communication and its personalization(bringing communication services to each user) - these are two interrelated problems that are successfully solved at this stage of human development by telecommunication specialists.

The further evolution of telecommunication technologies will go in the direction of increasing the speed of information transfer, intellectualization of networks and ensuring the mobility of users.

high speeds. Necessary for the transmission of images, including television, the integration of various types of information in multimedia applications, the organization of communication between local, urban and territorial networks.

Intelligence. It will increase the flexibility and reliability of the network, make it easier to manage global networks. Thanks to the intellectualization of networks, the user ceases to be a passive consumer of services, turning into an active client - a client who will be able to actively manage the network by ordering the services he needs.

Mobility. Successes in the field of miniaturization of electronic devices, reduction of their cost create prerequisites for the global spread of mobile terminal devices. This makes it a real task to provide communication services to everyone at any time and in any place.

In conclusion, we note that the amount of information transmitted through the information and telecommunications infrastructure of the world is doubling every 2-3 years. New branches of the information industry are emerging and successfully developing, the information component of the economic activity of market entities and the influence of information technologies on the scientific, technical, intellectual potential and health of nations. The beginning of the 21st century is seen as the era of the information society, requiring for its effective development creation of a global information and telecommunications infrastructure, the pace of development of which should be ahead of the pace of development of the economy as a whole. At the same time, the creation of the Russian information and telecommunications infrastructure should be considered as the most important factor in the rise of the national economy, the growth of business and intellectual activity of society, and the strengthening of the country's authority in the international community.

(Document)

Gitin V.Ya., Kochanovsky L.N. Fiber Optic Transmission Systems (Document)

Lectures - Fiber Optic Transmission Systems (Lecture)

Sharvarko V.G. Fiber optic communication lines (Document)

Degtyarev A.I., Tezin A.V. Fiber Optic Transmission Systems (Document)

Fokin V.G. Fiber Optic Transmission Systems (Document)

Ivanov V.A. Lectures: Measurements on fiber optic transmission systems (Document)

Okosi T. Fiber Optic Sensors (Document)

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Content

Introduction
Main part

History of the development of communication lines
Design and characteristics optical cables connections
2. Optical fibers and features of their manufacture
3. Optical cable designs
Basic requirements for communication lines
Advantages and disadvantages of optical cables

Conclusion
Bibliography

Introduction
Today, more than ever, the regions of the CIS countries need communication, both quantitatively and qualitatively. The leaders of the regions are primarily concerned about the social aspect of this problem, because the telephone is a matter of prime necessity. Communication also affects the economic development of the region, its investment attractiveness. At the same time, telecommunications operators, who spend a lot of effort and money to support the decrepit telephone network, are still seeking funds for the development of their networks, for digitization, and the introduction of fiber-optic and wireless technologies.

At this point in time, there is a situation where almost all major Russian departments are carrying out a large-scale modernization of their telecommunications networks.

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

Using fiber optic communication, the amount of transmitted information increases dramatically compared to such widespread means as satellite communications 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 appearance of optical quantum generator- laser. The word laser is made up of the first letters of the phrase Light Amplification by Emission of Radiation - light amplification by induced radiation. Laser systems operate in the optical wavelength range. If frequencies are used for cable transmission - megahertz, and for waveguides - gigahertz, then for laser systems the visible and infrared spectrum of the optical wave range (hundreds of gigahertz) is used.

The guide system for fiber-optic communication systems are dielectric waveguides, or fibers, as they are called because of the small transverse dimensions and method of obtaining. At the time when the first fiber was produced, the attenuation was on 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 the 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. Optical fibers with an attenuation of 0.2 dB/km at a wavelength of 1.55 µm were obtained.

Advances in the technology of obtaining light guides with low losses stimulated work on the creation of fiber optic communication lines.

Optical fiber communication lines have the following advantages over conventional cable lines:

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

Significantly higher bandwidth.

Small weight and overall dimensions. This reduces the cost and time of laying the optical cable.

Complete electrical isolation between the input and output of the communication system, so no common transmitter and receiver grounding is required. You can repair the optical cable without turning off the equipment.

Absence short circuits, as a result of which optical fibers can be used to cross hazardous areas without fear of short circuits, which are the cause of a fire in areas with combustible and flammable media.

Potentially low cost. Although optical fibers are made from ultra-clear glass with impurities of less than a few parts per million, their cost is not high when mass-produced. In addition, the production of optical fibers does not use such expensive metals as copper and lead, the reserves of which on Earth are limited. The cost is electrical lines The demand for 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) around the world. Currently, fiber optic cables and transmission systems for them are produced by many countries of the world.

Particular attention is paid here and abroad 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 possibility of transmitting a large flow of information over the required distances with large lengths of regeneration sections. Already now there are fiber optic lines for a large number of channels with a regeneration section length of 100 ... 150 km. Recently, 1.6 million km are manufactured annually in the USA. optical fibers, with 80% of them in a single-hearth version.

Modern domestic fiber optic cables of the second generation have been widely used, the production of which has been mastered by the domestic cable industry, they include cables of the 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 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 exchanges, and on the subscriber section of the network, both analog (for example, to organize a television channel) and digital transmission systems can be used. .

The maximum length of the linear paths of the main 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 intrazonal primary network can be no more than 600 km. With an average length of 200 km. Maximum length of city trunk lines for various systems transmission is 80...100 km.
Man has five senses, but one of them is especially important - this is vision. Through the eyes, a person perceives most of the information about the world around him 100 times more 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 the light source and the process of light modulation. He actually built what today we call an optical communication line or an optical communication system, including a transmitter (source), a modulator, an optical cable line and a receiver (eye). Having defined as modulation the transformation of a mechanical signal into an optical one, 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 a different kind for further processing in the receiver.

Such processing may be, for example, the transformation

of the light image in the eye into a sequence of electrical impulses

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

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

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 imperfection of the cable design, underground cable communication lines soon gave way to overhead ones. The first long-distance overhead 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, about 10 thousand km long. In 1939, the world's largest high-frequency telephone line Moscow-Khabarovsk, 8300 km long, was put into operation.

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

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

In 1882-1884. in Moscow, Petrograd, Riga, Odessa, the first urban telephone networks in Russia were built. In the 90s of the last century, the first cables, numbering up to 54 wires, were suspended on the city telephone networks of Moscow and Petrograd. In 1901, the construction of an 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 urban telephone cables with air-paper insulation and twisted in pairs. In 1900-1902. a successful attempt was made to increase the transmission range by artificially increasing the inductance of cables by including inductors in the circuit (Pupin's proposal), as well as the use of conductive cores with a ferromagnetic winding (Kruppa'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 starting from 1912-1913. mastering the production of electronic lamps. In 1917, V. I. Kovalenkov developed and tested a telephone amplifier using electronic tubes on the line. In 1923, a telephone connection was made with amplifiers on the Kharkov-Moscow-Petrograd line.

In the 1930s, the development of multichannel transmission systems began. Subsequently, the desire to expand the range of transmitted frequencies and increase the bandwidth of the lines led to the creation of new types of cables, the so-called coaxial. But their mass production dates back only to 1935, by the time new high-quality dielectrics such as escapon, high-frequency ceramics, polystyrene, styroflex, etc. appeared. These cables allow the transfer of energy at a current frequency of up to several million hertz and allow 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, organized only telegraph communications, and only 100 years later, in 1956, an underwater coaxial trunk was built between Europe and America for multichannel telephony.

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

The creation of a fiber light guide and the obtaining of continuous generation of a semiconductor laser played a decisive role in the rapid development of fiber-optic communication. By the beginning of the 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 communication, computer technology, the control and management system for technological processes, etc.

In Russia and other countries, urban and long-distance fiber-optic communication lines have been laid. They are given 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 quartz glass optical fibers (light guides) twisted according to a certain system, enclosed in a common protective sheath. If necessary, the cable may contain power (strengthening) and damping elements.

Existing OKs according to their purpose can be classified into three groups: main, zonal and urban. Underwater, object and installation OK are allocated in 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 information throughput. A single-mode fiber with a core and cladding of 8/125 µm is used. Wavelength 1.3...1.55 µm.

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

City OK are applied as connecting 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). Wavelength 0.85 and 1.3 µm. These lines, as a rule, operate without intermediate linear regenerators.

Submarine OK intended for communication through large water barriers. They must have high mechanical tensile strength and have reliable moisture-resistant coatings. It is also important for submarine communications to have low attenuation and long regeneration lengths.

Object OKs serve to convey information within an object. This includes office and video telephony, internal network cable television, as well as on-board information systems of mobile objects (aircraft, ship, etc.).

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

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

The light guide has a two-layer design and consists of a core and a cladding with different refractive indices. The core serves to transmit electromagnetic energy. Shell Purpose - Creation better conditions reflections at the "core - shell" interface and protection from interference from the surrounding space.

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

Outside the light guide there is a protective coating to protect it from mechanical influences and apply colors. The protective coating is usually made in two layers: first, an organosilicon compound (SIEL), and then an epoxy acrylate, fluoroplastic, nylon, polyethylene, or varnish. Overall fiber diameter 500...800 µm

Three types of optical fibers are used in existing optical fiber designs: stepped with a core diameter of 50 μm, gradient with a complex (parabolic) refractive index profile 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 manufacture of optical fibers, 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 the absorption and scattering of light. To obtain OF with low losses and attenuation, it is necessary to get rid of impurities so that there is a chemically pure glass.

At present, the most widely used method for creating OF with low losses is by chemical vapor deposition.

Obtaining OF by chemical vapor deposition is carried out in two stages: a two-layer quartz preform is manufactured and a fiber is drawn from it. The workpiece is made 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 high temperatures (1500...1700°C), pure quartz is deposited in layers on the inner surface of the tube. Thus, the entire internal 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 the collapse occurs and the tubular billet is transformed into a solid cylindrical billet. The pure deposited quartz then becomes the core of the optical fiber with a refractive index , and the tube itself acts as a shell with a refractive index . The drawing of the fiber from the workpiece and its winding on the receiving drum is carried out at the glass softening temperature (1800...2200°C). More than 1 km of optical fiber is obtained from a preform 1 m long.
Dignity this method is not only obtaining OF 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 titanium, germanium, boron, phosphorus or other reagents. Depending on the additive used, the refractive index of the fiber may vary. So, germanium increases, and boron reduces the refractive index. By selecting the recipe 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 pattern of change over the cross section of the fiber core.

Optical cable designs

OK constructions are mainly determined by the purpose and scope of their application. In this regard, there are many constructive options. Currently, a large number of types of cables are being developed and manufactured in various countries.

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

concentric stranded cables
shaped core cables
flat cables belt type.

The cables of the first group have a traditional twisted concentric core, similar to electric cables. Each subsequent winding of the core has six more fibers compared to 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 figured plastic core in the center with grooves in which the optical fibers are placed. The grooves and, accordingly, the fibers are located along the helicoid, and therefore they do not experience a longitudinal effect on the gap. Such cables can contain 4, 6, 8 and 10 fibers. If you need to have a cable large capacity, then several primary modules are applied.

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

In optical cables except OB , usually has the following elements:

power (reinforcing) rods that take on the longitudinal load, at break;
fillers in the form of continuous plastic threads;
reinforcing elements that increase the resistance of the cable under mechanical stress;
outer protective sheaths that protect the cable from the penetration of moisture, vapors harmful substances and external mechanical influences.

In Russia, various types and designs of OK are manufactured. For the organization of multi-channel communication, mainly four- and eight-fiber cables are used.

Are of interest OK French production. They, as a rule, are completed from unified modules consisting of a plastic rod with a diameter of 4 mm with ribs along the perimeter and ten OBs located along the periphery of this rod. Cables contain 1, 4, 7 such modules. Outside, the cables have an aluminum and then a polyethylene sheath.
The American cable, widely used on the GTS, is a stack of flat plastic tapes containing 12 OFs. The cable can have from 4 to 12 tapes containing 48-144 fibers.

In England, an experimental power transmission line was built with phase wires containing OF for technological communication along power lines. There are four OBs in the center of the power line wire.

Suspended OK are also used. They have a metal cable embedded in the cable sheath. Cables are intended for suspension along overhead line supports and walls of buildings.

For underwater communications, OK is designed, as a rule, with an outer armor cover made of steel wires (Fig. 11). In the center is a module with six OBs. The cable has a copper or aluminum tube. Current is supplied through the “tube-water” circuit remote power supply to underwater unattended amplification points.

Basic requirements for communication lines

In general, the requirements for a highly developed modern technology telecommunications 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 communications;
broadband and suitability for the transmission of various types of modern information (television, telephony, data transmission, broadcasting, transmission of newspaper pages, etc.);
protection of circuits from mutual and external interference, as well as from lightning and corrosion;
stability of the electrical parameters of the line, stability and reliability of communication;
efficiency of the communication system as a whole.

An intercity cable line is a complex technical structure, consisting of a huge number of elements. Since the line is designed for long-term operation (tens of years) and uninterrupted operation of hundreds and thousands of communication channels must be ensured on it, then to all elements of linear cable equipment, and primarily to cables and cable accessories included in the linear signal transmission path are high requirements. The choice of the type and design of the communication line is determined not only by the process of energy propagation along the line, but also by the need to protect adjacent RF circuits from mutual interfering influences. Cable dielectrics are selected based on the requirement to provide the greatest communication range in RF channels with minimal losses.

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

Predominant development of coaxial systems, which make it possible to organize powerful communication beams and transmit television programs over long distances via a single-cable communication system.
Creation and implementation of promising communication OKs 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 make it possible to automate production.
Introduction of aluminum, steel and plastic sheaths instead of lead. The sheaths must be airtight and ensure the stability of the electrical parameters of the cable throughout the entire service life.
Development and introduction into production of economical designs of cables for intrazonal communication (single-coaxial, single-quad, armorless).
Creation of shielded cables that reliably protect the information transmitted through them from external electromagnetic influences and thunderstorms, in particular cables in two-layer shells of the aluminum-steel and aluminum-lead types.
Increasing the electrical strength of the insulation of communication cables. A modern cable must simultaneously have 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.

Advantages of optical cables and their scope

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);
low losses and, accordingly, large lengths of broadcast sections (30...70 and 100 km);
small overall dimensions and weight (10 times less than electric cables);
high protection from external influences and crosstalk;
reliable safety technology (no sparks and short circuits).

The disadvantages of optical cables include:

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

Advantages and disadvantages of fiber optic communication
Advantages of open communication systems:

Higher ratio of received signal power to radiated power with smaller apertures of transmitter and receiver antennas.
Better spatial resolution with smaller transmitter and receiver antenna apertures
Very small dimensions of the transmitting and receiving modules used for communication over distances up to 1 km
Good communication secrecy
Development of an unused part of the spectrum of electromagnetic radiation
No need to obtain permission to operate the communication system

Disadvantages of open communication systems:

Low suitability for radio broadcasting due to the high directivity of the laser beam.
High required pointing accuracy of transmitter and receiver antennas
Low efficiency of optical emitters
Relatively high level noise in the receiver, due in part to the quantum nature of the optical signal detection process
Influence of Atmospheric Characteristics on Communication Reliability
Possibility of hardware failure.

Advantages of guiding communication systems:

The possibility of obtaining optical fibers with low attenuation and dispersion, which makes it possible to make distances between repeaters large (10 ... 50 km)
Small diameter single fiber cable
Permissibility of fiber bending under small radii
Low weight of optical cable with high information throughput
Low cost fiber material
The possibility of obtaining optical cables that do not have electrical conductivity and inductance
Negligible crosstalk

High communication secrecy: signal tapping is only possible with a direct connection to a separate fiber
Flexibility in implementing the required bandwidth: optical fibers various types allows you to replace electrical cables in digital communication systems of all levels of the hierarchy
Possibility of continuous improvement of the communication system

Disadvantages of guiding communication systems:

Difficulty in joining (splicing) optical fibers
The need to lay additional electrically conductive cores in an optical cable to provide power to remotely controlled equipment
The sensitivity of optical fiber to the effects of water when it enters the cable
Optical fiber sensitivity to ionizing radiation
Low efficiency of optical radiation sources with limited radiation power
Difficulties in Implementing the Multiple Access (Parallel) Access Mode Using a Time Division Bus
High noise level in the receiver

Directions of development and application of fiber optics

Wide horizons open practical application OK and fiber-optic transmission systems in such sectors of the national economy as radio electronics, computer science, communications, computer technology, space, medicine, holography, mechanical engineering, nuclear energy, etc. Fiber optics is developing in six areas:

multichannel information transmission systems;
cable TV;
local computer networks;
sensors and systems for collecting, processing and transmitting information;
communications and telemechanics on high-voltage lines;
equipment and installation of mobile objects.

Multichannel FOTS are beginning to be widely used on the backbone and zonal communication networks of the country, as well as for the device of connecting lines between urban exchanges. This is explained by the large information capacity of OK and their high noise immunity. Underwater optical highways are especially efficient and economical.

The use of optical systems in cable television provides high image quality and significantly expands the possibilities of information service for individual subscribers. In this case, a custom reception system is implemented and subscribers are provided with the opportunity to receive images of newspaper pages, magazine pages and reference data from the library and educational 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 unite computing centers into a single information system with high bandwidth, improved quality and security from unauthorized access.

Recently, a new direction in the development of fiber-optic technology has appeared - the use of the mid-infrared wavelength range of 2 ... 10 microns. It is expected that losses in this range will not exceed 0.02 dB/km. This will allow communication over long distances with regeneration sites up to 1000 km. The study of fluorine and chalcogenide glasses with additions of zirconium, barium, and other compounds possessing supertransparency 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 soliton mode of optical pulse propagation, when a pulse can propagate without changing its shape or periodically change its shape during propagation along a fiber. The use of this phenomenon in optical fibers will significantly increase the amount of transmitted information and the communication range without the use of repeaters.

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

When building FOCL subscriber networks, in addition to the traditional structure of a radial-nodal type telephone network, it is envisaged to organize ring networks that ensure cable savings.

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

In the third generation of FOTS, it is supposed to use the conversion of speech signals into optical ones directly with the help of acoustic transducers. An optical telephone has already been developed and work is underway to create fundamentally new automatic telephone exchanges that switch 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 integrated multi-purpose network is being created, including various types of information transmission (telephony, television, data transmission of computers and automated control systems, video telephone, phototelegraph, transmission of newspaper pages, messages from banks, etc.). A digital PCM channel with a transmission rate of 64 Mbps (or 32 Mbps) was adopted as a unified one.

For wide application QA and VOSP need to solve a number of problems. These primarily include the following:

study of systemic issues and determination of technical and economic indicators of the use of OK on communication networks;
mass industrial production of single-mode fibers, light guides and cables, as well as optoelectronic devices for them;
increasing moisture resistance and reliability of OK through the use of metal shells and hydrophobic filling;
mastering the infrared wavelength range of 2...10 µm and new materials (fluoride and chalcogenide) for the manufacture of light guides that allow communication over long distances;
creation local networks for computer technology and informatics;
development of testing and measuring equipment, reflectometers, testers necessary for the production of OK, configuration and operation of FOCL;
mechanization of laying technology and automation of OK installation;
improving the technology of industrial production of fiber light guides and OK, reducing 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 of OK;
creation of an integrated subscriber network of multi-purpose;
the 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 units of PCM channel-forming equipment using integrated optics elements;
creation of optical regenerators without converting optical signals into electrical ones;
improvement of transmitting and receiving optoelectronic devices for communication systems, development of coherent reception;
development effective methods and power supply devices for intermediate regenerators for zonal and backbone communication networks;
optimization of the structure of various sections of the network, taking into account the peculiarities of using systems on 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.

Conclusion
At present, wide horizons have opened up for the practical application of OK and fiber-optic transmission systems in such sectors of the national economy as radio electronics, computer science, communications, computer technology, space, medicine, holography, mechanical engineering, nuclear energy, 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 service for individual subscribers.

Fiber-optic sensors are capable of operating in aggressive environments, are reliable, small in size and not subject to electromagnetic influences. They allow you to evaluate at a distance various physical quantities (temperature, pressure, current, etc.). Sensors are used in the oil and gas industry, security and fire alarm systems, automotive technology, etc.

It is very promising to use OK on high-voltage power lines (TL) for the organization of technological communications 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.

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

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

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1. A brief overview of the development of communication lines

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

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 across the Northern Dvina and in 1879 across the Caspian Sea between Baku and Krasnovodsk. In 1866, the transatlantic cable telegraph line between France and the United States was put into operation.

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

In the 1930s, the development of multichannel transmission systems began. Subsequently, the desire to expand the range of transmitted frequencies and increase the bandwidth of the lines led to the creation of new types of cables, the so-called coaxial. But their mass production dates back only to 1935, when new high-quality dielectrics such as escapon, high-frequency ceramics, polystyrene, styroflex, etc. appeared. These cables allow the transmission of energy at a frequency of currents up to several million hertz and allow them to transmit 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, organized only telegraph communications. And only 100 years later, in 1956, an underwater coaxial line was built between Europe and America for multichannel telephone communication.

In Ukraine and other countries, urban and long-distance fiber-optic communication lines have been laid. They are given a leading place in the scientific and technological progress of the communications industry.

2. Communication lines and main properties of FOCL

On the present stage The development of society in the conditions of scientific and technological progress is continuously increasing the amount of information. As shown by theoretical and experimental (statistical) studies, the output of the communications industry, expressed in the amount of transmitted information, increases in proportion to the square of the growth of the gross national product of the national economy. This is determined by the need to expand the relationship between the various links of the national economy, as well as an increase in the amount of information in the technical, scientific, political and cultural life of society. The requirements for the speed and quality of the transfer of various information are increasing, the distances between subscribers are increasing. Communication is necessary for the operational management of the economy and the work of state bodies, to increase the country's defense capability and meet the cultural and everyday needs of the population.

In the era of the scientific and technological revolution, communication has become an integral part of the production process. It is used to control technological processes, electronic computers, robots, industrial enterprises, etc. An indispensable and one of the most complex and expensive communication elements are communication lines (LS), through which information electromagnetic signals are transmitted from one subscriber (station, transmitter, regenerator, etc.) to another (station, regenerator, receiver, etc.) .) and back. It is obvious that the efficiency of communication systems is largely determined by the quality of LS, their properties and parameters, as well as the dependence of these quantities on the frequency and the impact of various factors, including the interference of external electromagnetic fields.

There are two main types of drugs: lines in the atmosphere (radar radio links) and guide transmission lines (communication lines).

A distinctive feature of guide communication lines is that the propagation of signals in them from one subscriber (station, device, circuit element, etc.) to another is carried out only through specially created circuits and LAN paths that form guide systems designed to transmit electromagnetic signals in a given direction with due quality and reliability.

Currently, communication lines transmit signals from direct current to the optical frequency range, and the operating wavelength range extends from 0.85 microns to hundreds of kilometers.

There are three main types of LS: cable (CL), air (VL), fiber-optic (FOCL). Cable and overhead lines refer to wire lines, in which the guide systems are formed by “conductor-dielectric” systems, and fiber-optic lines are dielectric waveguides, the guide system of which consists of dielectrics with different refractive indices.

Fiber-optic communication lines are systems for transmitting light signals in the microwave range of waves from 0.8 to 1.6 microns over optical cables. This type of communication lines is considered as the most promising. The advantages of FOCL are low losses, high bandwidth, small weight and overall dimensions, saving non-ferrous metals, and a high degree of protection from external and mutual interference.

3. Basic requirements for communication lines

cable optical telephone microwave

In general, the requirements imposed by highly developed modern telecommunication technology on 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 communications;

Broadband and suitability for the transmission of various types of modern information (television, telephony, data transmission, broadcasting, transmission of newspaper pages, etc.);

protection of circuits from mutual and external interference, as well as from lightning and corrosion;

stability of the 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:

1. The predominant development of coaxial systems, which make it possible to organize powerful communication bundles and transmit television programs over long distances via a single-cable communication system.

2. Creation and implementation of promising communication OCs 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 automation of production.

5. Development and introduction into production of economical designs of cables for intrazonal communication (single-coaxial, single-quad, armorless).

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 shells of the aluminum-steel and aluminum-lead type.

7. Increasing the electrical strength of the insulation of communication cables. A modern cable must simultaneously have 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.

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