Optical communication lines

Optical communication lines are data transmission channels over fiber optics, in which information is transmitted by light pulses. They provide high speed, long range and protection from interference, which is why they are used for the backbone networks of banks and companies.

What is an optical communication line

An optical communication line (FOL) is a system for transmitting data over a fiber optic cable. Inside the cable there are thin glass or plastic fibers along which light from a transmitting device propagates. A laser source turns an electrical signal into light pulses, and at the receiving end a photodetector returns them to electrical form. Unlike copper lines, optical fiber is not afraid of electromagnetic interference, provides gigabit speeds over tens of kilometers and practically does not lose the signal. This makes an FOL the basis of corporate and backbone networks.

How fiber optics work

Optical fiber consists of a core, along which the light travels, a cladding that reflects the beam back into the core, and a protective coating. By the number of modes, single-mode fiber (small core, one beam, long lines up to tens of kilometers) and multimode fiber (large core, many beams, short distances inside buildings and campuses) are distinguished. A cable combines several fibers and protective elements: armor, moisture protection and strength threads. Typical connectors of optical lines are LC, SC and MPO, and fiber splicing is performed by fusion welding with loss control.

Why optics is chosen

Optics beats twisted pair in range (kilometers instead of 100 meters), speed (up to hundreds of Gbps) and reliability: it is not affected by electromagnetic interference, thunderstorms and neighboring cables. Data, voice and video streams are transmitted over fiber, which is important for banking networks and video surveillance systems. Optical lines do not emit the signal outward, which reduces the risk of unauthorized data extraction, and a fiber break is easily detected with special instruments. The disadvantages include the higher cost of installation, splicing and equipment compared to copper.

Fiber optic line layout

An optical line is built according to the scheme: signal source → transmitting device (SFP module) → optical cable → receiving device. At the ends of the line there are switches with optical ports or media converters converting optics to copper. To distribute the signal to several directions, optical distribution frames and splitters are used. In server rooms and cabinets, fiber is laid in cable organizers, and in backbones between buildings the cable is laid in conduits or along poles. Routes are documented: for each line the length, losses and connection scheme are recorded.

Maintenance and diagnostics of fiber optic lines

Uninterrupted operation of optical lines is ensured by regular checks. The signal level is measured with a reflectometer (OTDR), which detects the location of a break and losses at fiber joints, and losses at connectors are controlled with an optical tester. Dusty connectors are cleaned with special wipes, damaged patch cords and pigtails are replaced. Measurement results are entered into the line passports: the wavelength, losses and laying scheme are recorded, which simplifies modernization. For inter-building backbones, protection against mechanical damage, spare fibers and route documentation are provided.