Cleaning Fiber-Optic Connectors - Cisco ASR 9000 Series Installation Manual

Chapter 2 Installing Line Cards in the Cisco ASR 9000 Series Router

Cleaning Fiber-Optic Connectors

Fiber-optic connectors are used to connect two fibers together. When these connectors are used in a
communication system, proper connection becomes a critical factor. They can be damaged by improper
cleaning and connection procedures. Dirty or damaged fiber-optic connectors can result in
communication that is inaccurate or not repeatable.
Fiber-optic connectors differ from electrical or microwave connectors. In a fiber-optic system, light is
transmitted through an extremely small fiber core. Because fiber cores are often 62.5 microns or less in
diameter, and dust particles range from a tenth of a micron to several microns in diameter, dust and any
other contamination at the end of the fiber core can degrade the performance of the connector interface
where the two cores meet. Therefore, the connector must be precisely aligned and the connector interface
must be absolutely free of foreign material.
Connector loss, or insertion loss, is a critical performance characteristic of a fiber-optic connector.
Return loss is also an important factor. Return loss specifies the amount of reflected light: the lower the
reflection, the better the connection. The best physical contact connectors have return losses of better
than –40 dB, but –20 to –30 dB is more common.
The connection quality depends on two factors: the type of connector and the proper cleaning and
connection techniques. Dirty fiber connectors are a common source of light loss. Keep the connectors
clean at all times, and keep the dust plugs or covers installed when the connectors are not in use.
Before installing any type of cable or connector, use a lint-free alcohol pad from a cleaning kit to clean
the ferrule, the protective tube or cone that surrounds the fiber core, and the end-face surface of the fiber
core.
As a general rule, any time you detect a significant, unexplained loss of light, clean the connectors. To
clean the optical connectors, use a CLETOP fiber optic cleaning cassette and follow the manufacturer's
usage instructions.
If a CLETOP cleaning cassette is not available, follow these steps:
Use a lint-free tissue soaked in 99 percent pure isopropyl alcohol and gently wipe the end-face of the
Step 1
fiber core. Wait for five seconds for the surfaces to dry and wipe the surfaces a second time.
Use clean, dry, oil-free compressed air to remove any residual dust from the connector.
Step 2
Warning Because invisible laser radiation may be emitted from the aperture of the port when no cable is
connected, avoid exposure to laser radiation and do not stare into open apertures. Statement 70
Step 3 Use a magnifying glass or inspection microscope to inspect the ferrule at angle. Do not look directly into
the aperture. If you detect any contamination, repeat
For more information about cleaning fiber-optic connectors, as well as SFP/XFP transceivers, see
Inspection and Cleaning Procedures for Fiber- Optic Connections.
Cisco ASR 9000 Series Aggregation Services Router Ethernet Line Card Installation Guide
Step 1 and Step 2.
Cables and Connectors
2-73