Calculating Power Budget For Fiber-Optic Cable; Calculating Power Margin For Fiber-Optic Cable; Table 48: Estimated Values For Factors Causing Link Loss - Juniper ACX5048 Manual

ACX5048 and ACX5096 Universal Access Router

Calculating Power Budget for Fiber-Optic Cable

Calculating Power Margin for Fiber-Optic Cable

96
Use the information in this topic and the information in Supported Network Interface
Standards by Transceiver for ACX, M, MX, and T Series Routers or Supported Network
Interface Standards by Transceiver for PTX Series Routers to calculate the power budget
and power margin for fiber-optic cables.
To calculate the power budget and power margin, perform the following tasks:
Calculating Power Budget for Fiber-Optic Cable on page 96
1.
2. Calculating Power Margin for Fiber-Optic Cable on page 96
To ensure that fiber-optic connections have sufficient power for correct operation, you
need to calculate the link's power budget, which is the maximum amount of power it
can transmit. When you calculate the power budget, 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 the worst-case levels. To calculate the worst-case estimate of power budget (P
you assume minimum transmitter power (P
P = P – P
B T R
The following hypothetical power budget equation uses values measured in decibels
(dB) and decibels referred to one milliwatt (dBm):
P = P – P
B T R
P = –15 dBm – (–28 dBm)
B
P = 13 dB
B
After calculating a link's power budget, you can calculate the power margin (P
represents the amount of power available after subtracting attenuation or link loss (LL)
from the power budget (P
P = P – LL
M B
A P greater than zero indicates that the power budget is sufficient to operate the receiver.
M
Factors that can cause link loss include higher-order mode losses (HOL), modal and
chromatic dispersion, connectors, splices, and fiber attenuation.
lists an estimated amount of loss for the factors used in the following sample calculations.
For information about the actual amount of signal loss caused by equipment and other
factors, refer to vendor documentation.

Table 48: Estimated Values for Factors Causing Link Loss

Link-Loss Factor
Higher-order mode losses
) and minimum receiver sensitivity (P
T
). A worst-case estimate of P
B
Estimated Link-Loss Value
Single-mode—None
Multimode—0.5 dB
), which
M
assumes maximum LL:
M
Table 48 on page 96
Copyright © 2015, Juniper Networks, Inc.
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