Juniper CBL-PWR-10AC-STR-IT Manuel D’Utilisation
Table 26: Estimated Values for Factors Causing Link Loss (continued)
Estimated Link-Loss Value
Link-Loss Factor
Single-mode—0.5 dB/km
Multimode—1 dB/km
Fiber attenuation
The following example uses the estimated values in
to calculate
link loss (
LL
) for a 2-km-long multimode link with a power budget (
P
B
) of 13 dB:
•
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
The power margin (
P
M
) is calculated as follows:
P
M
= P
B
– LL
P
M
= 13 dB – 2 km (1.0 dB/km) – 5 (0.5 dB) – 2 (0.5 dB) – 0.5 dB [HOL] – 1 dB [CRM]
P
M
= 13 dB – 2 dB – 2.5 dB – 1 dB – 0.5 dB – 1 dB
P
M
= 6 dB
The following sample calculation for an 8-km-long single-mode link with a power budget
(
(
P
B
) of 13 dB uses the estimated values from
to calculate link loss
(
LL
) as the sum of fiber attenuation (8 km @ 0.5 dB/km, or 4 dB) and loss for seven
connectors (0.5 dB per connector, or 3.5 dB). The power margin (
P
M
) is calculated as
follows:
P
M
= P
B
– LL
P
M
= 13 dB – 8 km (0.5 dB/km) – 7(0.5 dB)
P
M
= 13 dB – 4 dB – 3.5 dB
P
M
= 5.5 dB
In both examples, the calculated power margin is greater than zero, indicating that the
link has sufficient power for transmission and does not exceed the maximum receiver
input power.
link has sufficient power for transmission and does not exceed the maximum receiver
input power.
Related
Documentation
•
•
Copyright © 2012, Juniper Networks, Inc.
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M7i Multiservice Edge Router Hardware Guide