Calculating Power Margin For Fiber-Optic Cable For M Series, Mx Series, And T Series Routers; Table 33: Estimated Values For Factors Causing Link Loss - Juniper M320 Hardware Manual

M320 Router Hardware Guide
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Calculating Power Margin for Fiber-Optic Cable for M Series, MX Series, and T Series Routers

262
at the worst-case levels. To calculate the worst-case estimate of power budget (
you assume minimum transmitter power (
P = P – P
B T R
The following hypothetical power budget equation uses values measured in decibels
(dB) and decibels referred to one milliwatt (dBm):
P = P – P
B T R
P = –15 dBm – (–28 dBm)
B
P = 13 dB
B
M320 Power System Description on page 33
M320 Site Preparation Checklist Requirements on page 41
General Electrical Safety Warnings for M Series, MX Series, and T Series Routers on
page 231
Site Electrical Wiring Guidelines for M Series, MX Series, and T Series Routers on page 249
After calculating a link's power budget you can calculate the power margin (
represents the amount of power available after subtracting attenuation or link loss (
from the power budget (
P
P = P – LL
M B
A P greater than zero indicates that the power budget is sufficient to operate the receiver.
M
Factors that can cause link loss include higher-order mode losses (HOL), modal and
chromatic dispersion, connectors, splices, and fiber attenuation. Table 33 on page 262
lists an estimated amount of loss for the factors used in the following sample calculations.
For information about the actual amount of signal loss caused by equipment and other
factors, refer to vendor documentation.

Table 33: Estimated Values for Factors Causing Link Loss

Link-Loss Factor
Higher-order mode losses
Modal and chromatic dispersion
Connector
P ) and minimum receiver sensitivity (
T
). A worst-case estimate of
B
Estimated Link-Loss Value
Single-mode—None
Multimode—0.5 dB
Single-mode—None
Multimode—None, if product of bandwidth and distance
is less than 500 MHz-km
0.5 dB
), which
P
M
assumes maximum
P LL
M
Copyright © 2010, Juniper Networks, Inc.
),
P
B
P ):
R
LL )
: