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An optical fiber connector terminates the end of an optical fiber, and enables quicker connection and disconnection than splicing. The connectors mechanically couple and align the cores of fibers so that light can pass. Better connectors lose very little light due to reflection or misalignment of the fibers.
Optical fiber connectors are used to join optical fibers where a connect/disconnect capability is required. The basic connector unit is a connector assembly. A connector assembly consists of an adapter and two connector plugs. Due to the polishing and tuning procedures that may be incorporated into optical connector manufacturing, connectors are generally assembled onto optical fiber in a supplier’s manufacturing facility. However, the assembly and polishing operations involved can be performed in the field, for example, to make cross-connect jumpers to size.
Optical fiber connectors are used in telephone company central offices, at installations on customer premises, and in outside plant applications. Connectors are used to connect equipment and cables, or to cross-connect cables within a system.
Most optical fiber connectors are spring-loaded. The end faces of the fibers in the two connectors are pressed together, resulting in a direct glass to glass or plastic to plastic contact. This avoids a trapped layer of air between two fibers, which would increase connector insertion loss and reflection loss.
Every fiber connection has two values :
Measurements of these parameters are now defined in IEC standard 61753-1. The standard gives five grades for insertion loss from A (best) to D (worst), and M for multimode. The other parameter is return loss, with grades from 1 (best) to 5 (worst).
A variety of optical fiber connectors are available, but SC and LC connectors are the most common types of connectors on the market. Typical connectors are rated for 500–1,000 mating cycles. The main differences among types of connectors are dimensions and methods of mechanical coupling. Generally, organizations will standardize on one kind of connector, depending on what equipment they commonly use. Different connectors are required for multimode, and for single-mode fibers.
In datacom and telecom applications nowadays small connectors (e.g., LC) and multi-fiber connectors (e.g., MTP) are replacing the traditional connectors (e.g., SC), mainly to provide a higher number of fibers per unit of rack space.
Features of a good connector design:
Outside plant applications may involve locating connectors underground in subsurface enclosures that may be subject to flooding, on outdoor walls, or on utility poles. The closures that enclose them may be hermetic, or may be free-breathing. Hermetic closures will subject the connectors within to temperature swings but not to humidity variations unless they are breached. Free-breathing closures will subject them to temperature and humidity swings, and possibly to condensation and biological action from airborne bacteria, insects, etc. Connectors in the underground plant may be subjected to groundwater immersion if the closures containing them are breached or improperly assembled.
Depending on user requirements, housings for outside plant applications may be tested by the manufacturer under various environmental simulations, which could include physical shock and vibration, water spray, water immersion, dust, etc. to ensure the integrity of optical fiber connections and housing seals.
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