Calculating Power Margin For Fiber-Optic Cable For M Series, Mx Series, And T Series Routers; Table 51: Estimated Values For Factors Causing Link Loss - Juniper M7i Hardware Manual

M7i Multiservice Edge Router Hardware Guide
Calculating Power Margin for Fiber-Optic Cable for M Series, MX Series, and T Series
Routers
94
Calculating Power Margin for Fiber-Optic Cable for M Series, MX Series, and T Series
Routers on page 94
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.
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 51: Estimated Values for Factors Causing Link Loss

Link-Loss Factor
Higher-order mode losses
Modal and chromatic dispersion
Connector
Splice
Fiber attenuation
The following example uses the estimated values in
link loss ( ) for a 2-km-long multimode link with a power budget (
LL
Fiber attenuation for 2 km @ 1.0 dB/km= 2 dB
Loss for five connectors @ 0.5 dB per connector = 5(0.5 dB) = 2.5 dB
Loss for two splices @ 0.5 dB per splice =2(0.5 dB) = 1 dB
Higher-order mode loss = 0.5 dB
Clock recovery module = 1 dB
). 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
0.5 dB
Single-mode—0.5 dB/km
Multimode—1 dB/km
P
M
assumes maximum
P LL
M
Table 51 on page 94
Table 51 on page 94 to calculate
) of 13 dB:
P
B
Copyright © 2019, Juniper Networks, Inc.
), which
LL )
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