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Fiber-Optic Connectors

Figure 14

SC-Type Fiber-Optic Connector

Plug

Keys

Cable

Light out

of fiber

Receptacle

Light into

fiber

Key slots

CWDM SFPs come in eight wavelengths that range from 1470 nm to 1610 nm. Color markings on the

devices identify the wavelength to which the Gigabit Ethernet channel is mapped. Specifications for

CWDM SFPs are at:

http://www.cisco.com/en/US/docs/interfaces_modules/transceiver_modules/installation/note/78_15160

.html

Fiber-Optic Connectors

Fiber-optic cable connectors can be damaged by improper cleaning and connection procedures. Dirty or

damaged fiber-optic connectors can result in communication that is not repeatable or inaccurate.

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

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 trapped 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 greater than

-40 dB, although -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 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 white tube around the fiber, and the end-face surface of the fiber.

As a general rule, whenever there is a significant, unexplained loss of light, clean the connectors.

Installation and Configuration Note for the Catalyst 4500 E-Series Supervisor Engine 6-E

78-18337-01