CHAPTER 10
Transceiver and Cable Specifications
•
Calculating Power Budget and Power Margin for Fiber-Optic Cables on page 131
•
Understanding Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion on page 133
•
Routing Engine Interface Cable and Wire Specifications for MX Series Routers on page 134
Calculating Power Budget and Power Margin for Fiber-Optic Cables
Use the information in this topic and the specifications for your optical interface to
calculate the power budget and power margin for fiber-optic cables.
TIP: You can use the Hardware Compatibility Tool to find information about
the pluggable transceivers supported on your Juniper Networks device.
To calculate the power budget and power margin, perform the following tasks:
1.
Calculating Power Budget for Fiber-Optic Cable on page 131
2.
Calculating Power Margin for Fiber-Optic Cable on page 132
Calculating Power Budget for Fiber-Optic Cable
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
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
131Copyright © 2017, Juniper Networks, Inc.
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