Juniper MX240 Hardware Manual page 210

MX240 Ethernet Services Router Hardware Guide
Table 38: Estimated Values for Factors Causing Link Loss (continued)
The following example uses the estimated values in Table 38 on page 181 to calculate
link loss (
The power margin (
P M = P B
P M = 13 dB
P M = 13 dB
P M = 6 dB
The following sample calculation for an 8 km-long single-mode link with a power
budget (
link loss (
for seven connectors (0.5 dB per connector, or 3.5 dB). The power margin (
calculated as follows:
P M = P B
P M = 13 dB
P M = 13 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.
182
Network Cable Specifications and Guidelines
Link-Loss Factor
Splice
Fiber attenuation
LL ) for a 2 km-long multimode link with a power budget (
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 loss = 0.5 dB
Clock recovery module = 1 dB
P M ) is calculated as follows:
LL
2 km (1.0 dB/km)
2 dB 2.5 dB
) of 13 dB uses the estimated values from Table 38 on page 181 to calculate
P B
LL ) as the sum of fiber attenuation (8 km @ 0.5 dB/km, or 4 dB) and loss
LL
8 km (0.5 dB/km)
4 dB 3.5 dB
Estimated Link-Loss Value
0.5 dB
Single-mode—0.5 dB/km
Multimode—1 dB/km
5 (0.5 dB) 2 (0.5 dB)
1 dB 0.5 dB 1 dB
7 (0.5 dB)
P B ) of 13 dB:
0.5 dB [HOL] 1 dB [CRM]
) is
P M