Juniper EX4500 Series, Руководство по оборудованию

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Table 26: Estimated Values for Factors Causing Link Loss (continued)
Sample (LL) Calculation Values Estimated Link-Loss Value Link-Loss Factor
•
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
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.
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