Fiber Optic Termination
There are a variety of ways in which to physically attach a fiber to a connector - fiber optic termination - each has its time and place. There is the standard Heat Cured
method, which is probably one of the first commercially viable ways of attaching fiber to a connector. The basic theory is to inject an empty connector body with a liquid epoxy, which will harden while 'baked' in an isometric heat sink (oven). Once 'cured,' the protruding fiber is scored (scribed) and then polished to completion. Though considered time consuming by today's standards, this method of termination still provides some of the most durable connectors available. With the vast improvement in epoxy technologies, the cure time has been reduced from several hours to that of several minutes. An offshoot of this method is the
3M Hot Melt
series. With the Hot Melt, a heat sensitive epoxy is preloaded into the connector at the factory, there is no need for mixing epoxies or injection needles. The epoxy is liquidized by the heat of a small 'oven' and after the fiber is threaded through the connector, the epoxy re-hardens as it cools. After cooling, the fiber is scribed and polished to completion. The only concern with these connectors is using them in extremely hot environments. The epoxy will soften under extreme heat (>185* F) and the fiber may become loose or piston. In South Florida and the Caribbean where we work, using Hot Melts inside sealed outdoor security camera enclosures may pose a concern under the hot summer sun. One other slight draw back, both of these heat-cured connectors require electric power for their heat sources. Otherwise, they are a fast and convenient 'heat cured' connector.
More recent versions of a cured connector are Anaerobic Connector and the UV Light
cured connector. With the Anaerobic connector, a base epoxy is injected into the empty connector, while the connector's end face and the bare fiber is dipped into a 'primer'. As the coated fiber is threaded through the connector, the primer acts as a sealant cutting off oxygen to the base epoxy which in turn allows the epoxy to harden. Hence the name Anaerobic Connector (lacking oxygen). These connectors are considered fast and convenient, though they can be a bit messy if proper housekeeping is not maintained. Like the heat cured and the 3M Hot Melt, once the epoxy is cured (a mere few seconds), the fiber protruding from the connector is scribed and polished to completion. The UV Light cured connector has the same general concept but uses a UV activated epoxy for curing. Hence you need a UV lamp and electrical power nearby.
One final method of securing fiber to a connector body is by Mechanical Crimping. In this style of connector, the connector's end face is generally factory finished and the fiber is cleaned, cleaved and threaded into the connector. Once fully
seated inside the connector, the fiber is mechanically crimped onto the connector body. Whether by Unicam, V-Groove, or some other form of alignment, the fiber is held in place by some compression mechanism
on the fiber and/or outer coating. With these connectors, great care must be taken in the cleaving process to ensure proper exposed bare fiber lengths as well as a clean square cleave. Index matching gel
inside the connector body minimizes the likelihood of an air gap between the fiber strand and the inside edge of the end face. These connectors are fast and convenient though a bit costlier. For Waveguide,
the school is still out as to whether these type of connectors can hold up under the constant vibrations found within the Marine industry. |
