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8-14 Cleaning Connections for Accurate Measurements
Inspecting 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 minimize exces-
sive 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 sig-
nal and increased reflections, resulting in poor return
loss.
Because fiber-optic connectors are susceptible to dam-
age that is not immediately obvious to the naked eye,
bad measurements can be made without the user even
being aware of a connector problem. Although micro-
scopic examination and return loss measurements are
the best way to ensure good connections, they are not
always practical. An awareness of potential problems,
along with good cleaning practices, can ensure that
optimum connector performance is maintained. With
glass-to-glass interfaces, it is clear that any degradation
of a ferrule or the end of the fiber, any stray particles, or
finger oil can have a significant effect on connector per-
formance.
Figure 8-4
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 soft nickel-silver ferrule.
Figure 8-5
shows a dirty fiber end from neglect or per-
haps improper 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 8-6
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 damage on one connector end
can be transferred to another good connector that
comes in contact with it.
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