Juniper EX4650 Series

•
Calculate the power budget. See “Calculating the Fiber-Optic Cable Power Budget for EX Series Devices”
on page 69.
To calculate the worst-case estimate for the power margin (P
M
) for the link:
1. Determine the maximum value for link loss (LL) by adding estimated values for applicable link-loss
factors—for example, use the sample values for various factors as provided in Table 28 on page 70
(here, the link is 2 km long and multimode, and the (P
B
) is 13 dBm):
Table 28: Estimated Values for Factors Causing Link Loss
Sample (LL) Calculation ValuesEstimated Link-Loss ValueLink-Loss Factor
•
0.5 dBm
•
0 dBm
•
Multimode— 0.5 dBm
•
Single mode— None
Higher-order mode losses (HOL)
•
0 dBm
•
0 dBm
•
Multimode— None, if product of
bandwidth and distance is less than
500 MHz/km
•
Single mode— None
Modal and chromatic dispersion
This example assumes 5 connectors.
Loss for 5 connectors:
(5) * (0.5 dBm) = 2.5 dBm
0.5 dBmConnector
This example assumes 2 splices. Loss
for two splices:
(2) * (0.5 dBm) = 1 dBm
0.5 dBmSplice
This example assumes the link is 2
km long. Fiber attenuation for 2 km:
•
(2 km) * (1.0 dBm/km) = 2 dBm
•
(2 km) * (0.5 dBm/km) = 1 dBm
•
Multimode— 1 dBm/km
•
Single mode— 0.5 dBm/km
Fiber attenuation
1 dBm1 dBmClock Recovery Module (CRM)
NOTE: For information about the actual amount of signal loss caused by equipment and other
factors, see your vendor documentation for that equipment.
2. Calculate the (P
M
) by subtracting (LL) from (P
B
):
P
B
– LL = P
M
70