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General Information
Cleaning Connections for Accurate Measurements
Figure 1-8. Damage from improper cleaning.
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 end of the fiber.
Also, some early gels were designed for use with the FC, non-contacting con-
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.
