Juniper QFX10002 Hardware Manual page 92

Table 36: Estimated Values for Factors Causing Link Loss
Link-Loss Factor
Fiber attenuation
The following sample calculation for a 2-km-long multimode link with a power budget (P
the estimated values from
attenuation (2 km @ 1 dB/km, or 2 dB) and loss for five connectors (0.5 dB per connector, or 2.5 dB) and
two splices (0.5 dB per splice, or 1 dB) as well as higher-order mode losses (0.5 dB). The power margin
(P ) is calculated as follows:
M
P = P – LL
M B
P = 13 dB – 2 km (1 dB/km) – 5 (0.5 dB) – 2 (0.5 dB) – 0.5 dB
M
P = 13 dB – 2 dB – 2.5 dB – 1 dB – 0.5 dB
M
P = 7 dB
M
The following sample calculation for an 8-km-long single-mode link with a power budget (P
uses the estimated values from
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
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.
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Estimated Link-Loss Value
Single mode—0.5 dB/km
Multimode—1 dB/km
Table 36 on page 82. This example calculates link loss (LL) as the sum of fiber
Table 36 on page 82. This example calculates link loss (LL) as the sum of
) is calculated as follows:
M
(Continued)
83
) of 13 dB uses
B
) of 13 dB
B