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Maintenance
Cleaning Connections for Accurate Measurements
• Keep connectors covered when not in use.
• Use fusion splices on the more permanent critical nodes. Choose the best connector possible. Re-
place 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 equipment are a good indication that you have
good connections. Since return loss and insertion loss are key factors in determining optical con-
nector 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 con-
nectors 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 pol-
ished 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 best physically contacting connectors
have return losses better than 50 dB, although 30 to 40 dB is more common.
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