Juniper Networks EX8208 manual 122

Complete Hardware Guide for EX8208 Ethernet Switches

Table 51: Estimated Values for Factors Causing Link Loss (continued)

Link-Loss Factor	Estimated Link-Loss Value		Sample (LL) Calculation Values
Connector	0.5 dBm		This example assumes 5 connectors.
			Loss for 5 connectors:
			5(0.5 dBm) = 2.5 dBm
Splice	0.5 dBm		This example assumes 2 splices. Loss for
			two splices:
			2(0.5 dBm) = 1dBm
Fiber attenuation	•	Multimode—1 dBm/km	This example assumes the link is 2 km
	•	Single mode—0.5 dBm/km	long. Fiber attenuation for 2 km:
			• 2 km(1.0 dBm/km) = 2 dBm
			• 2 km( 0.5 dBm/km) = 1 dBm
Clock Recovery Module (CRM)	1 dBm		1 dBm

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 ) by subtracting (LL) from (P ):

MB

P – LL = P

BM

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 = 6 dBm

M

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

122 Copyright © 2010, Juniper Networks, Inc.