GarrettCom 1008 - Manual (Page 33)

Magnum 1000 Workgroup Hubs Installation and User Guide (04/02)
27
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Magnum 3000 Stackable Hub
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3.3.8 Power Budget Calculations for Magnum 1000 Series RPM’s with 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 Magnum products, 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 µm (M.m) is 2.8 dB/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
The following data has been collected from component manufacturer’s (HP’s and
Siemens’) web sites and catalogs to provide guidance to network designers and
installers.
Fiber
Port
Module
Speed,
Std.
Mode
Std.
km
fdx
(hdx)
Wave
-
length
nm
Cable
Size
µm
X’mitr
Output
P
T ,
dB
R’cvr
Sens.
P
R ,
dB
Worst
OPB,
dB
Worst*
distance
Km, fdx
typical
OPB,
dB
typical*
distance
Km, fdx
RPM-MST,
MSC
10 Mb
FL
Multi-
mode
2
(2)
850
62.5/125
100/140
50/125
-15.0
-9.5
-19.5
-31
-31
-31 14
19.5
9.5
5
5.9
3.4
17
23.5
13.5
6
7
4.8
RPM-
SMF (ST)
10 Mb
FL
Single-
mode
10
(5)
1300 9/125 -30 -39 7 14 13 26
* Note: The use of either multi-mode or single-mode fiber to operate at 100Mbps speed
over long distances (i.e., in excess of 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, i.e. the
full-duplex (factory default) setting for 100Mbps fiber ports must be used,
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)
3.3.9 Rack-mounting
Installation of a Magnum
1000 Series Hub in a 19” rack is a
simple procedure. The units are 1U
(1.75”) high. When properly installed, the front-mounted LED status indicators should