3-11
Reference
Fiber-Optic Connectors
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 mini-
mize excessive scratching and wear. While minor wear is not a prob lem if th e
glass face is not affected, scratches or grit can cause the glass fibe r to move
out of alignment. Also, if unkeyed connect ors a re us ed, th e nic kel sil ver can be
pushed onto the glass surface. Scratches, fiber movement, or glass contamina-
tion will cause loss of signal and increased reflection s, res ult ing i n poo r re tu rn
loss.
Inspecting Connectors
Because fiber-optic connectors are susceptible to damage that is not immedi-
ately 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 fibe r, any stray
particles, or finger oil can have a significant e ffect on connector performance.
Where many repeat connections are required, u se of a connector saver or
patch cable is recommended.
Figure3-4 shows the end of a clean fiber-optic cable. The dark circle in the
center of the micrograph is the fiber’s 125 µm core and cladding which carries
the light. The surrounding area is the so ft nickel-silver ferrule. Figure 3-5
shows a dirty fiber end from neglect or perhaps improper cleaning. Material is
smeared and ground into the end of the f ib er c au si ng l igh t s c att erin g an d po or
reflection. Not only is the precision polish lost, but this ac tion can grind off the
glass face and destroy the connector.
Figure3-6 sho w s phy s ical damage to the glass fiber end caused by either
repeated connections made without removing loose particles or usi ng
improper cleaning tools. When severe, the damage 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 3-15.