Coaxial communication

Cables

It consists of two cylindrical conductors inserted one into another. The central copper conductor covered with the plastic isolating material over which there is the second conductor — a copper braid or aluminum foil with a braid from copper tinned pro-reducing dies is most often used. Distinguish two types of the coaxial cable: thin and thick. The thin coaxial cable is capable to transmit a signal to distance to 180 meters without its noticeable distortion caused by attenuation. Equipment manufacturers developed special marking for different types of cables. The thin coaxial cable belongs to group which is called RG-58 family, its wave resistance is equal 50 Ohms. Wave resistance is the electromagnetic characteristic determining the cable resistance to alternating current of operating frequency of a cable. Wave resistance does not depend on length of the coaxial cable and completely is defined by its construction. The thick coaxial cable — rather rigid cable with a diameter about 1 cm. Sometimes it is called "standard Ethernet" as it was the first cable type applied in a popular network architecture of Ethernet. The copper core of this cable is thicker, than at the thin coaxial cable. And the more thickly lived at a cable, the signal is capable to overcome bigger distance. Therefore, the thick coaxial cable transmits signals further, than thin — to 500 meters. Therefore the thick coaxial cable is used sometimes as the main cable which connects several small networks, built on the thin coaxial cable.

Standards

In 1995-1996. The European committee on standardization in electrical equipment (CENELEC) adopts EN50117 standard on "The coaxial cables used in cable distribution networks" (Coaxial cables used in cabled distribution networks). It laid the foundation of the regulating documentation on coaxial cables, the broadband multimedia networks intended for the organization. First of all the standard sets a size range of diameters on isolation for distribution and main cables: 6.9; 8.8; 13.5; 19.4; 23 and 29 mm. In it the work area of frequencies of such cables is also legalized: 5 — 862 MHz, being considered as basic in Europe till 1996. EN50117 standard consists of four parts:

• "General specification";
• "Test methods and measurements";
• "Group specification on distribution and main cables";
• "Specification on subscriber's cables".

The International Electrotechnical Commission (an IEC or IEC) is also engaged in standardization of coaxial cables for broadband distribution networks. The subcommittee of SC46A of this organization published structure of the developed standards. They differ from documents of CENELEC a little, but the structure remains the same. The draft standard consisting of six interconnected parts was approved in May, 2001. Then in November of the same year the subcommittee approved merge of two series of standards: on coaxial cables for local area networks (LAN) and on coaxial cables for distribution networks (TV). As a result IEC 61196 should remain one series of standards known as. Now the IEC standards on coaxial cables for distribution networks are in a discussion stage in member countries of an IEC. When the merge of two series of standards stated above happens, it will mean transition to qualitatively new level in the international standardization of coaxial cables.

See Also

SCS

Fiber optic communication