Black Box LPH240A-H, Operation Manual

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Chapter 3: Installation
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3.8.5 Power Budget Calculations, Fiber Media
Receiver Sensitivity and Transmitter Power are the parameters
necessary to compute the power budget. To calculate the power budget
of different fiber media installations using Black Box Heavy Duty Edge
Switches, the following equations should be used:
OPB (Optical Power Budget) = P
T
(min) - P
R
(min)
where P
T
= Transmitter Output Power, and P
R
= Receiver
Sensitivity
Worst case OPB = OPB - 1dB(for LED aging) - 1dB(for insertion loss)
Worst case distance = {Worst case OPB, in dB} / [Cable Loss, in
dB/Km]
where the “Cable Loss” for 62.5/125 and 50/125
μ
m (m.m.) is
2.8dB/km,
and the “Cable Loss” for 100/140 (Multi-mode) is 3.3 dB/km,
and the “Cable Loss” for 9/125 (Single-mode) is 0.5 dB/km
* Note: The use of either multi-mode or single-mode fiber to operate at
100Mbps speed over long distances (i.e., over approx. 400 meters) can
be achieved only if the following factors are both applied:
•
The 100Mb fiber segment must operate in full-duplex (FDX)
mode, and
•
The worst-case OPB of the fiber link must be greater than
the fiber cable’s passive Attenuation.
(Attenuation = Cable loss + LED aging loss + Insertion loss +
safety factor)