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The soft core, while allowing precise centering, is also the chief liability of the connector. The soft
material is easily damaged. Care must be taken to minimize excessive scratching and wear.
While minor wear is not a problem if the glass face is not affected, scratches or grit can cause the
glass fiber to move out of alignment. Also, if unkeyed connectors are used, the nickel silver can
be pushed onto the glass surface. Scratches, fiber movement, or glass contamination will cause
loss of signal and increased reflections, resulting in poor return loss.
Inspecting Connectors
Because fiber-optic connectors are susceptible to damage that is not immediately obvious to the
naked eye, poor measurements result without the user being aware. Microscopic examination
and return loss measurements are the best way to ensure good measurements. Good cleaning
practices can help ensure that optimum connector performance is maintained. With glass-to-
glass interfaces, any degradation of a ferrule or the end of the fiber, any stray particles, or finger
oil can have a significant effect on connector performance. Where many repeat connections are
required, use of a connector saver or patch cable is recommended.
Figure 6-5
shows the end of a clean fiber-optic cable. The dark circle in the center of the micro-
graph is the fiber's 125 µm core and cladding which carries the light. The surrounding area is the
soft nickel-silver ferrule.
Figure 6-6
cleaning. Material is smeared and ground into the end of the fiber causing light scattering and
poor reflection. Not only is the precision polish lost, but this action can grind off the glass face
and destroy the connector.
Figure 6-7
shows physical damage to the glass fiber end caused by either repeated connections
made without removing loose particles or using improper cleaning tools. When severe, the dam-
age of one connector end can be transferred to another good connector endface that comes in
contact with the damaged one. Periodic checks of fiber ends, and replacing connecting cables
after many connections is a wise practice.
The cure for these problems is disciplined connector care as described in the following list and in
"Cleaning Connectors" on page
Cleaning Connections for Accurate Measurements
shows a dirty fiber end from neglect or perhaps improper
6-15.
Maintenance
6-11
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