3Com 7000 manual Example, Appendix D Cabling Requirements

114APPENDIX D: CABLING REQUIREMENTS

Table 27 Insertion Losses for Mating Unlike Fiber Types - Transmitting Fiber

Receiving	Numerical
Fiber Size	Aperture	50 µ m	50 µ m	62.5 µ m	85 µ m	100 µ m
		0.20	0.22	0.275	0.26	0.29
50 µm	0.20	0.0	0.4	2.2	3.8	5.7
50 µm	0.22	0.0	0.0	1.6	3.2	4.9
62.5 µm	0.275	0.0	0.0	0.0	1.0	2.3
85 µm	0.26	0.0	0.0	0.1	0.0	0.8
100 µm	0.29	0.0	0.0	0.0	0.0	0.0
Table 28 Typical Losses for Typical Connectors, Cables, and Splices
Type of Insertion			Loss
SC connector			.6 dB
ST connector (ceramic)			.6 dB
ST connector (plastic)			1.0 dB
ST connector (stainless steel)			.7 dB
62.5/125 cable			1.0 to 3.0 dB maximum per km, depending
			on cable quality (nominal 2.0 dB)
8/125 cable			.5 dB/km (AT&T Lightguide)
Bypass switch (currently not			2.5 dB maximum
available in single mode)
Fusion splice			1 to 3 dB depending on type used (use .3 dB)

Example

Suppose that a link consisting of one km of 62.5/125 fiber with a maximum attenuation rating of 1.75 dB/km is transmitting into one km of 50/125 fiber with a maximum attenuation rating of 3 dB/km. The fibers are joined using a fusion splice rated at 0.3 dB and the link contains one in-line ST connector rated at 0.6 dB.

The following calculation would arrive at the link loss attenuation value for this linked fiber:

62.5µ m	+ 50µ m	+ splice	+ ST con-	+ insertion	= Total link
cable loss	cable loss	loss	nector loss	loss*	attenuation
1 km(1.75	+1 km(3	+0.3 dB	+0.6 dB	+2.2 dB	=7.85 dB
dB/km)	dB/km)

* for mating unlike fiber types