Juniper ACX1000 User Manual

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
B
),
you assume minimum transmitter power (P
T
) and minimum receiver sensitivity (P
R
):
P
B
= P
T
– P
R
The following hypothetical power budget equation uses values measured in decibels
(dB) and decibels referred to one milliwatt (dBm):
P
B
= P
T
– P
R
P
B
= –15 dBm – (–28 dBm)
P
B
= 13 dB
Calculating Power Margin for Fiber-Optic Cable
After calculating a link's power budget, you can calculate the power margin (P
M
), which
represents the amount of power available after subtracting attenuation or link loss (LL)
from the power budget (P
B
). A worst-case estimate of P
M
assumes maximum LL:
P
M
= P
B
– LL
P
M
greater than zero indicates that the power budget is sufficient to operate the receiver.
Factors that can cause link loss include higher-order mode losses, modal and chromatic
dispersion, connectors, splices, and fiber attenuation. Table 29 on page 78 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 29: Estimated Values for Factors Causing Link Loss
Estimated Link-Loss ValueLink-Loss Factor
Single-mode—None
Multimode—0.5 dB
Higher-order mode losses
Single-mode—None
Multimode—None, if product of bandwidth and distance is less than 500
MHz-km
Modal and chromatic dispersion
0.5 dBConnector
0.5 dBSplice
Single-mode—0.5 dB/km
Multimode—1 dB/km
Fiber attenuation
Copyright © 2017, Juniper Networks, Inc.78
ACX1000 and ACX1100 Universal Access Router

Juniper ACX1000 Specifications

General

Brand	Juniper
Model	ACX1000
Category	Network Router
Language	English