HP 86037B, Instruction Manual

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5-25
Maintenance
Cleaning Connections for Accurate Measurements
nectors, using small glass spheres. When used with contacting connectors,
these glass balls can scratch and pit the fiber. If an index matching gel or oil
must be used, apply it to a freshly cleaned connector, make the measurement,
and then immediately clean it off. Never use a gel for longer-term connections
and never use it to improve a damaged connector. The gel can mask the extent
of damage and continued use of a damaged fiber can transfer damage to the
instrument.
• When inserting a fiber-optic cable into a connector, gently insert it in as
straight a line as possible. Tipping and inserting at an angle can scrape material
off the inside of the connector or even break the inside sleeve of connectors
made with ceramic material.
• When inserting a fiber-optic connector into a connector, make sure that the fi-
ber end does not touch the outside of the mating connector or adapter.
• Avoid over tightening connections.
Unlike common electrical connections, tighter is not better. The purpose of
the connector is to bring two fiber ends together. Once they touch, tightening
only causes a greater force to be applied to the delicate fibers. With connec-
tors that have a convex fiber end, the end can be pushed off-axis resulting in
misalignment and excessive return loss. Many measurements are actually
improved by backing off the connector 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 con-
nector possible. Replace connecting cables regularly. Frequently measure the
return loss of the connector to check for degradation, and clean every connec-
tor, 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 indica-
tion 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 pro-