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Getting Started
Cleaning Connections for Accurate Measurements
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 equipment are a good indication that
you have good connections. 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 mea-
surement. The quality of the polish establishes the difference between the "PC"
(physical contact) and the "Super PC" connectors. Most connectors today are physi-
cal 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 some-
times 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 best physically contacting connectors have return losses
better than 50 dB, although 30 to 40 dB is more common.
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