Juniper QFX5200 - Calculating Power Budget and Power Margin for Fiber-Optic Cables; How to Calculate Power Budget for Fiber-Optic Cables; How to Calculate Power Margin for Fiber-Optic Cables

Calculang Power Budget and Power Margin for Fiber-Opc Cables
IN THIS SECTION
How to Calculate Power Budget for Fiber-Opc Cables | 81
How to Calculate Power Margin for Fiber-Opc Cables | 81
Use the informaon in this topic and the specicaons for your opcal interface to calculate the power
budget and power margin for ber-opc cables.
TIP: You can use the Hardware Compability Tool to nd informaon about the pluggable
transceivers supported on your Juniper Networks device.
To calculate the power budget and power margin, perform the following tasks:
How to Calculate Power Budget for Fiber-Opc Cables
To ensure that ber-opc connecons have sucient power for correct operaon, 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 esmate of
power budget (P
B
), you assume minimum transmier power (P
T
) and minimum receiver sensivity (P
R
):
P
B
= P
T
– P
R
The following hypothecal power budget equaon uses values measured in decibels (dB) and decibels
referred to one milliwa (dBm):
P
B
= P
T
– P
R
P
B
= –15 dBm – (–28 dBm)
P
B
= 13 dB
How to Calculate Power Margin for Fiber-Opc Cables
Aer calculang a link's power budget, you can calculate the power margin (P
M
), which represents the
amount of power available aer subtracng aenuaon or link loss (LL) from the power budget (P
B
). A
worst-case esmate of P
M
assumes maximum LL:
81