as provided in
Table 67 on page 104
(here, the link is 2 km long and multimode, and
the (
P
B
) is 13 dBm):
Table 67: Estimated Values for Factors Causing Link Loss
Sample (LL) Calculation Values
Estimated Link-Loss Value
Link-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 dBm
Connector
This example assumes 2 splices. Loss for
two splices:
(2) * (0.5 dBm) = 1 dBm
0.5 dBm
Splice
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 dBm
1 dBm
Clock 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
(13 dBm) – (0.5 dBm [HOL]) – ((5) * (0.5 dBm)) – ((2) * (0.5 dBm)) – ((2 km) *
(1.0 dBm/km)) – (1 dB [CRM]) = P
M
13 dBm – 0.5 dBm – 2.5 dBm – 1 dBm – 2 dBm – 1 dBm = P
M
13 dBm – 0.5 dBm – 2.5 dBm – 1 dBm – 2 dBm – 1 dBm = P
M
P
M
= 6 dBm
The calculated power margin is greater than zero, indicating that the link has sufficient
power for transmission. Also, the power margin value does not exceed the maximum
receiver input power. Refer to the specification for your receiver to find the maximum
receiver input power.
Copyright © 2015, Juniper Networks, Inc.
104
EX4300 Switch Hardware Guide
Summary of Contents for EX4300
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