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Getting Started
Cleaning Connections for Accurate Measurements
Figure 1-6. 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 connectors, 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 con-
nector. 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 fiber 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 con-
nector is to bring two fiber ends together. Once they touch, tightening only causes a
greater force to be applied to the delicate fibers. With connectors 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 connector
possible. Replace connecting cables regularly. Frequently measure the return loss of
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