Juniper QFX5100, Hardware Manual

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GR-253-CORE (Section 4.3) and International Telecommunications Union (ITU)
document G.957.
When chromatic dispersion is at the maximum allowed, its effect can be considered as
a power penalty in the power budget. The optical power budget must allow for the sum
of component attenuation, power penalties (including those from dispersion), and a
safety margin for unexpected losses.
Related
Documentation
Calculating the Fiber-Optic Cable Power Budget for a QFX Series Device on page 93
•
•
Calculating the Fiber-Optic Cable Power Margin for a QFX Series Device on page 93
Calculating the Fiber-Optic Cable Power Budget for a QFX Series Device
Calculate the link's power budget when planning fiber-optic cable layout and distances
to ensure that fiber-optic connections have sufficient power for correct operation. The
power budget is the maximum amount of power the link 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 for fiber-optic cable power budget (P
B
) for the
link:
1.
Determine values for the link's minimum transmitter power (P
T
) and minimum receiver
sensitivity (P
R
). For example, here, (P
T
) and (P
R
) are measured in decibels, and decibels
are referenced to one milliwatt (dBm).
P
T
= –15 dBm
P
R
= –28 dBm
NOTE: See the specifications for your transmitter and receiver to find the
minimum transmitter power and minimum receiver sensitivity.
2.
Calculate the power budget (PB) by subtracting (P
R
) from (PT):
–15 dBm – (–28 dBm) = 13 dBm
Related
Documentation
Understanding QFX Series Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion
on page 91
•
•
Calculating the Fiber-Optic Cable Power Margin for a QFX Series Device on page 93
Calculating the Fiber-Optic Cable Power Margin for a QFX Series Device
Calculate the link's power margin when planning fiber-optic cable layout and distances
to ensure that fiber-optic connections have sufficient signal power to overcome system
losses and still satisfy the minimum input requirements of the receiver for the required
93 Copyright © 2014, Juniper Networks, Inc.
Chapter 9: Cable Specifications