Juniper CBL-M40-PWR-AU 用户手册
Fiber-Optic and Network Cable Guidelines
M40 Internet Router Hardware Guide
52
Table 16 lists the estimated amount of loss for factors that cause link loss.
Table 16: Estimating Link Loss
In the following sample calculation for a 2 km-long multimode link with a power budget (
P
B
)
of 13 dB, the link loss (
LL
) is the sum of the following factors:
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
The power margin is 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]
PM = 13 dB – 2 dB – 2.5 dB – 1 dB – 0.5 dB – 1 dB
P
P
M
= 6 dB
In the following sample calculation for an 8 km-long single-mode link with a power budget
(P
B
) of 13 dB, the link loss (
LL
) is 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:
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.
has sufficient power for transmission and does not exceed the maximum receiver input
power.
Link-Loss Factor
Estimated Link-Loss Value
Higher-order mode losses
Single-mode—None
Multimode—0.5 dB
Multimode—0.5 dB
Modal and chromatic
dispersion
dispersion
Single-mode—None
Multimode—None, if product of bandwidth and distance is less than 500
MHz–km
Multimode—None, if product of bandwidth and distance is less than 500
MHz–km
Connector
0.5 dB
Splice
0.5 dB
Fiber attenuation
Single-mode—0.5 dB/km
Multimode—1 dB/km
Multimode—1 dB/km