Optical Fiber Cable Termination, Splicing Procedures and Standards

We have discussed the Duct cable installation, Direct buried cable installation and Aerial cable installation in separate posts in this blog. Once the optical fiber cable reaches the Telephone exchange building, they need to be terminated and spliced with other cables for proper routing and distributing to desired locations.

The outdoor cables coming to the Telephone exchange building shall be joined with the fiber optic indoor cables having a function at the termination box. The optical fiber cable and the fiber optic cords with connectors at the end shall be connected in the termination box that is to be installed either separately from the distribution frame in the telephone exchange.

optical fiber termination box

The OSP contractor in many cases by contract is responsible for the supply of cable rack for the Main distribution frame to termination box and optical distribution frame. The optical fiber cables shall be placed on the cable racks. The contractor will supply optical fiber cords as well. Some exchanges or remote terminal equipment building will have existing cable racks. In this case, a preliminary inspection and assurance from the concerned authority will help to reduce initial investment costs.

Optical fibers shall be properly protected in the termination box when they are exposed. It is the contractors’ responsibility to provide a detailed drawing of splice closures for different sizes of optical fiber cable.

Minimum splice loss shall be ensured by the splicing method employed to connect the optical fibers to the exchange. Generally, a splice loss value of less than 0.05 dB is considered as good. But the staff engaged in splicing the optical fibers will be skilled enough to bring the splice to close to 0.01 or 0.00. One of my staff Fukuoka-san was able to bring surprise to me with minimum splice loss in all the projects he involved with me.

Splice loss greatly depends on the geometrical characteristics of an optical fiber cable. The core clad concentricity error or mode field concentricity error, which the ITU-T now changed to core concentricity error is the main contributor to the splice loss. Splicing optical fibers from a reputed fiber manufacturer is an easy and relaxing job.

The coating materials on the fiber that is removed to splice the optical fibers must be removed from the splicing area without hazard to either optical fibers or to the personnel. The splicing tray or case shall be supported by proper brackets fixed to the walls in the manholes, hand-holes, and cable vault or trench as the case may be.

The splice trays shall be protected from accidental damage when a manhole is opened. For trunk cables installed aerially on the poles, the splicing case shall be installed to keep sufficient cable allowance on the pole and provide proper pole brackets for the excess fiber length.

The splicing case for the buried cable shall be accommodated in the manhole or hand-hole. The splice loss, we discussed here that depends greatly on the mode field diameter is a topic to be discussed in depth as we have observed upward signature in OTDR when the spliced location is analyzed using an OTDR. Probably by the end of next week, I will try to cover that theoretical aspect of splice loss and the importance of core concentricity error in splicing.

Related Articles

Design Principles of Fiber Optic Aerial Pole Route

General Notes on Fusion Splicing of Optical Fibers

Calculation of Pulling Tension of Fiber Optic Cable During Installation

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