Juniper EX4200-24T User Manual

When you calculate the power margin, you use a worst-case analysis to provide a margin
of error, even though all the parts of an actual system do not operate at worst-case
levels. A power margin (P
M
) greater than zero indicates that the power budget is sufficient
to operate the receiver and that it does not exceed the maximum receiver input power.
This means the link will work. A (P
M
) that is zero or negative indicates insufficient power
to operate the receiver. See the specification for your receiver to find the maximum
receiver input power.
Before you begin to calculate the power margin:
•
Calculate the power budget. See “Calculating the EX Series Switch Fiber-Optic Cable
Power Budget” on page 76.
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 39 on page 77 (here, the link is 2 km long and multimode, and
the (P
B
) is 13 dBm):
Table 39: 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
Thisexample assumes 2 splices. Lossfor
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.
77Copyright © 2017, Juniper Networks, Inc.
Chapter 7: Power Specifications and Requirements

Juniper EX4200-24T Specifications

General

Brand	Juniper
Model	EX4200-24T
Category	Switch
Language	English