Basic requirements for communication lines

 

In general, the requirements of a highly modern technology to the telecommunications long-distance communication lines, may be summarized as follows:

- Implementation of communication at 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 media (television, telephony, data transmission, broadcasting, transmission and front pages of newspapers, etc., as well as modern, interactive forms of communication..);

- Protection of circuits against mutual and external interference, as well as storms and corrosion (electrical cables and optical fiber cables with metal elements);

- The stability of the electrical parameters of the line (electric cables), optical parameters (optical cables), the stability and reliability of the communication;

- Cost communication system as a whole.

Cable lines (electrical and optical) DLD is a complex technical structure, consisting of a large number of elements. Since the line is designed for continuous operation (tens of years and above) and her smooth operation of hundreds and thousands of channels should be provided (thread) connections, then all elements of linear-cable equipment, and first of all the cables and cable accessories included into a linear signal path, high demands. Selecting the type and design of the link is determined by not only the process of propagation of energy along the line, but also the need to protect the adjacent RF circuit from mutual interferences (electrical cable). Cable dielectrics are selected on the basis of the requirements to ensure maximum communication range in the HF channels with minimal losses.

In accordance with this cable machinery developed in the following areas:

1) Development of coaxial systems to organize the powerful beams of communication and transmission on single-cable connection system, cable television programs.

2) Development and implementation of advanced communication OK for a high number of channels and does not require for its production of scarce metals (copper, lead).

3) The widespread introduction in the cable equipment of plastics (polyethylene, polystyrene, polypropylene, etc.), Have good electrical and mechanical characteristics and to automate production.

4) The introduction of aluminum, steel and plastic casings instead of lead. Skins should have the integrity and ensure the stability of the electrical parameters of the cable over the entire service life.

5) The development and introduction of cost-effective designs intra communication cables.

6) Creating a shielded cable, securely protecting transmitted information on them from external electromagnetic influences and thunderstorms, in particular cables in double membranes.

7) Increase of dielectric strength of cables of communication. Modern cable (electrical and optical cable with metal elements) should have the same time as the high-frequency properties of the cable, and the power of an electric cable, and capable of transmitting high-voltage currents for remote unattended power regeneration (amplifier) items over long distances.

 

The lines of communication and the basic properties of the fiber optic link

 

At the present stage of development of society in the conditions of scientific and technological progress continually increase the amount of information. As shown by theoretical and experimental (statistical) research, communication industry production, expressed in the amount of transmitted information increases in proportion to the square of the growth of the gross domestic product of the economy. This is determined by the need to expand the relationship between the various links of the national economy, as well as increasing the amount of information in the technical, scientific, political and cultural life of society. Increases the demands on the speed and quality of transmission of a variety of information, increasing the distance between callers. Communication is essential for the operational management of the economy and of public authorities to improve the country's defense and to meet cultural and social needs of the population.

In an era of scientific and technological revolution, communication has become an integral element of the production process. It is used for process control, electronic computers, robots, industrial enterprises t. D. An essential and one of the most complex and expensive coupling elements are link (LAN), which transmits the information electromagnetic signals from one subscriber (station transmitter, regenerator, etc.) to another (the station, the regenerator, and a receiver r. h.) and back. It is obvious that the effectiveness of the communication systems is largely determined by the quality of medicines, their properties and parameters, as well as the dependence of these quantities on the frequency and impact of various factors, including the third-party interferences of electromagnetic fields.

There are two main types of drugs: the line in the atmosphere (radio link RL) and the guide link (link). Below are the main types of opportunities and common rail communication systems (Table 1.1)

 

Table 1.1 Frequency-classification systems and radio guide

Frequency, Hz	Wavelength	The guide system	Radiofacilities
10^5	km	AL	RL
10^6	100 M	SC	RL
10^8	м	СС SWL	RL
10^9	дцм	CC SL	RRL
10^10	cm	-	RRL
10^11	mm	MW DW	-
10^12-10^14	IRL	**	**
10^14-10^15	OL	L	-
10^15-10^17	UVL	**	**

 

Note: * According to the bands conducted experimental work on the development in the field of telecommunications and radio.

A distinctive feature of the guide lines is that signals propagating therein from one user (station apparatus, the circuit element and the like. D.) To another is carried out only by specially created circuits and paths PM forming guide system for transmitting electromagnetic signals in a predetermined direction due to the quality and reliability.

Currently, communication links are transferred from the DC signals to an optical frequency range and the operating wavelength range extending from 0.85 microns to hundreds of kilometers.

There are three main types of drugs: Cable (TC), air (VL), optical fiber (fiber optic). Cable and overhead lines are wired lines in which the system guides the system image "conductor-insulator", and fiber-optic lines are dielectric waveguides, guiding system consisting of dielectrics with different refractive indices.

Fiber-optic lines are systems for transmitting light signals of the microwave wavelength range from 0.8 to 1.6 microns on optical cables. This type of links is seen as the most promising. The advantages of fiber optic links are low loss, high bandwidth, low weight and compact dimensions, the savings of non-ferrous metals, high degree of protection from external interference and. Below (Table 1.2) shows the comparative characteristics of different guides on the number of channel systems, as well as to the range.

Table 1.2- Number of communication channels for different guide systems

Guiding system	Frequency Hz	Possible number of telephone channels	Transmission system
Air line	10^5		В-12
Symmetrical cable	10^6		К-60; К-120 (And a number of joint venture PCM
Coaxial cable	10^8	1000-10 000	К-1920 (And a number of joint venture PCM)
The waveguide	10^11	100 000	К-3600
The light guide	10^14-10^15	100 000 000	К-10800, JV with PDH and SDH **

 

Note: JV with PDH and SDH ** - transmission system supporting PDH and SDH technology, working on the optical cable.

Conclusion: In view of the major requirements for the communication lines, and comparing the characteristics of the various communication lines (with the main fiber-optic properties) from the land-zone network Stepnogorsk Kokshetau proposed upgrade link based on optical cable.