Optical fiber cables are products that contain optical fibers and a power element located in a protective sheath. Additionally, depending on the operating conditions of the cable, it can be enhanced by armor (for example, for laying in the ground).
Optical cables are divided according to the conditions of use and purpose. Consider the main classification.
By appointment, they are divided into:
- trunk (divided into international and intercity);
- intraband (intercity and connecting);
- local (connecting, distribution and subscriber);
- intrasubject (station and subscriber).
According to the conditions of use, the optical cable is divided into:
- underground (directly into the ground, cable ducts, collectors, tunnels);
- air (communication support, power transmission lines, contact network);
- underwater (along the bottom of rivers and reservoirs, along the bottom of the seas and oceans).
Since fiber-optic cable (FOC) is not as durable as copper and aluminum cables we are used to, they are protected from external influences. Such effects include: temperature changes, water penetration, and mechanical stresses - bends, torsion, tension, shock, vibration, rotation, compression, etc.).
What an optical cable consists of:
- The outer shell is made of plastic to protect against external influences;
- Aramid threads for protection against squeezing and stretching;
- The inner plastic shell separating the optical module from the aramid filaments;
- The connecting tape, for a bunch of optical modules in one braid;
- Filling module - for forming the shape of the cable;
- Optical module - contains directly the optical fibers themselves. Usually, they have up to 8 fibers in one module, but sometimes more;
- Optical fibers - through which light signals are transmitted;
- Metal or fiberglass bar - the central element for strength, protects against stretching. Used in self-supporting cable;
- Hydrophobic aggregate - protects fibers from water penetration;
- Optical cable design.
What are the requirements for fiber optic cables?
There are certain requirements for the physicomechanical parameters of optical cables:
- high tensile strength;
- moisture resistance;
- buffer protection to reduce losses caused by mechanical stress of materials;
- operating temperature range from minus 40 to plus 50 centigrade;
- resistance to radiation exposure;
- good flexibility and the ability to lay on existing routes;
- resistance to aggressive environments;
- resistance to blows;
- simplicity of installation and laying;
- the term of work is at least 20 years.
In the process of manufacturing optical cables, it is important to consider the relative positions of power elements and optical fibers. Basically, two layout options are used:
- The reinforcing element is located in the center of the cable, and optical fibers around it;
- Optical fibers are located in the center, and the power element is around the fibers.