Juniper M320 Hardware Manual page 289

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Copyright © 2010, Juniper Networks, Inc.
Table 33: Estimated Values for Factors Causing Link Loss (continued)
Link-Loss Factor
Splice
Fiber attenuation
The following example uses the estimated values in Table 33 on page 262 to calculate
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
The power margin ( ) is calculated as follows:
P
M
P = P – LL
M B
P = 13 dB – 2 km (1.0 dB/km) – 5 (0.5 dB) – 2 (0.5 dB) – 0.5 dB [HOL] – 1 dB [CRM]
M
P = 13 dB – 2 dB – 2.5 dB – 1 dB – 0.5 dB – 1 dB
M
P = 6 dB
M
The following sample calculation for an 8-km-long single-mode link with a power budget
( ) of 13 dB uses the estimated values from Table 33 on page 262 to calculate link loss
P
B
( ) as the sum of fiber attenuation (8 km @ 0.5 dB/km, or 4 dB) and loss for seven
LL
connectors (0.5 dB per connector, or 3.5 dB). The power margin (
follows:
P = P – LL
M B
P = 13 dB – 8 km (0.5 dB/km) – 7(0.5 dB)
M
P = 13 dB – 4 dB – 3.5 dB
M
P = 5.5 dB
M
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.
M320 Power System Description on page 33
M320 Site Preparation Checklist Requirements on page 41
Appendix E: M320 Router Cable and Wire Guidelines and Specifications
Estimated Link-Loss Value
0.5 dB
Single-mode—0.5 dB/km
Multimode—1 dB/km
) of 13 dB:
P
B
) is calculated as
P
M
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