Telecommunication Room Terminations - LAN Wiring - page 183

emits hazardous levels of laser light, especially if you are using single-mode fiber.
Appropriate eye protection should be worn and appropriate precautions taken
when you are dealing with laser emitters that transmit above Hazard Level 1. ANSI
Z136.2 contains more information on these precautions. Even nonlaser light may
be a hazard if held close to the eye. A good rule is to never look into a fiber . The
fiber wavelengths are in the invisible infrared spectrum anyhow, so looking only
subjects you to a hazard, as you cannot see the light. The hazard exists even with
unterminated fiber ends, so treat them as you would terminated fiber. Although vis-
ible light testers are sometimes used during troubleshooting, you would be safer
when using these if you simply point the connector or fiber at your hand and look
for a dot of light, rather than trying to look directly at the fiber. Bad habits are hard
to break, so don't start one.
The tiny glass slivers that result from cutting, cleaving, and sometimes polish-
ing fibers are also an eye hazard. Always wear safety glasses when terminating fiber.
You also don't want to inhale any of the fiber dust, but you should be able to avoid
it when field-terminating fiber cables under normal circumstances.
See Chapter 11 for more information on fiber-optic installation practices.
Marking
As we discussed for station outlets, proper identification of TR terminations is cru-
cial to a high-quality, serviceable wiring installation. This includes a consistent
method of cable and termination numbering.
Each and every cable, termination fixture, patch panel, and cross-connect
should be clearly identified. EIA/TIA-606 provides a method of marking just about
everything in the telecommunications wiring world, with wiring terminations being
no exception. The guidelines call for each item to be marked with a unique identi-
fication that is clearly visible. That generally means you should use 3/8-in-high let-
tering and designate each cable termination and patch position in some orderly
fashion, such as with the TR number, cable number, position, etc.
Some connecting blocks make marking difficult, while others seem to have
marking panels as part of the design. Contrasting examples are 66 blocks and 110
blocks. Some older patch panels leave little room for markings, other than the small
factory-marked jack number. In a very small installation, this does not cause too
much difficulty, but larger installations require more detailed, explanatory markings.
You also may choose to use color to help designate wire termination areas. The
official colors for grouping different types of cable terminations are given in Chapter
14. The colors are defined in EIA/TIA-569-A, Commercial Building Standard for
Telecommunications Pathways and Spaces .