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Reference
Cleaning Connections for Accurate Measurements
Guidelines
Use the following guidelines to achieve the best possible performance when
making measurements on a fiber-optic system:
• Keep connectors covered when not in use.
• Use dry connections whenever possible.
• Never use metal or sharp objects to clean the connector and never scrape the
connector.
• Avoid matching gel and oils.
While these often work well on first insertion, they are great dirt magnets. The
oil or gel grabs and holds grit that is then ground into the fiber endface. Also,
some early gels were designed for use with the FC, non-contacting connec-
tors, 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 or adapter, gently insert it
in as straight a line as possible. Make sure the fiber end does not touch the out-
side of the mating connector or adapter. 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.
• Avoid over tightening connections.
Unlike common electrical connections, tighter is
not
better. The purpose of
the connector is to bring the endfaces of two fibers together. Once they touch,
tightening only causes a greater force to be applied to the delicate endfaces.
With some connectors, the end can set itself off-axis with a tight connection,
due to the curved face, resulting in misalignment and excessive return loss.
Many measurements are actually improved by backing off the connector pres-
sure. 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 connections covered when not in use.
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