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Cleaning Connections for Accurate Measurements 8-17
pressure. Also, if a piece of grit does happen to get by
the cleaning procedure, the tighter connection is more
likely to damage the glass. Tighten the connectors just
until the two fibers touch.
• Keep connectors covered when not in use.
• Use fusion splices on the more permanent critical nodes.
Choose the best connector possible. Replace connecting
cables regularly. Frequently measure the return loss of
the connector to check for degradation, and clean every
connector, every time.
All connectors should be treated like the high-quality
lens of a good camera. The weak link in instrument and
system reliability is often the inappropriate use and
care of the connector. Because current connectors are
so easy to use, there tends to be reduced vigilance in
connector care and cleaning. It takes only one missed
cleaning for a piece of grit to permanently damage the
glass and ruin the connector.
Measuring insertion loss and return loss
Consistent measurements with your lightwave equip-
ment are a good indication that you have good connec-
tions. Since return loss and insertion loss are key
factors in determining optical connector performance
they can be used to determine connector degradation.
A smooth, polished fiber end should produce a good
return-loss measurement. The quality of the polish
establishes the difference between the "PC" (physical
contact) and the "Super PC" connectors. Most connec-
tors today are physical contact which make glass-to-
glass connections, therefore it is critical that the area
around the glass core be clean and free of scratches.
Although the major area of a connector, excluding the
glass, may show scratches and wear, if the glass has
maintained its polished smoothness, the connector can
still provide a good low level return loss connection.
If you test your cables and accessories for insertion loss
and return loss upon receipt, and retain the measured
data for comparison, you will be able to tell in the future
if any degradation has occurred. Typical values are less
than 0.5 dB of loss, and sometimes as little as 0.1 dB of
loss with high performance connectors. Return loss is a
measure of reflection: the less reflection the better (the
larger the return loss, the smaller the reflection). The
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