Switch User Manual

Table 51: Estimated Values for Factors Causing Link Loss (continued)
Sample (LL) Calculation ValuesEstimated Link-Loss ValueLink-Loss Factor
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) = 1dBm
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
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.
Related Topics • Calculating the EX8200 Switch Fiber-Optic Cable Power Budget on page 120
• Optical Interface Support in EX8200 Switches on page 60
• Understanding EX8200 Switch Fiber-Optic Cable Signal Loss, Attenuation, and
Dispersion on page 106
Copyright © 2010, Juniper Networks, Inc.122
Complete Hardware Guide for EX8208 Ethernet Switches