Calculating The Fiber-Optic Cable Power Margin For A Qfx Series Device - Juniper QFX10016 Hardware Manual

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Calculating the Fiber-Optic Cable Power Margin for a QFX Series Device

132
To calculate the worst-case estimate for the fiber-optic cable power budget (P
link:
Determine values for the link's minimum transmitter power (P
1.
sensitivity (P ). For example, here, (P
R
are referenced to 1 milliwatt (dBm):
P = –15 dBm
T
P = –28 dBm
R
NOTE: See the specifications for your transmitter and receiver to find the
minimum transmitter power and minimum receiver sensitivity.
Calculate the power budget (P
2.
–15 dBm – (–28 dBm) = 13 dBm
Understanding QFX Series Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion
on page 130
Calculating the Fiber-Optic Cable Power Margin for a QFX Series Device on page 132
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
performance level. The power margin (P
attenuation or link loss (LL) has been subtracted from the power budget (P
When you calculate the power margin, 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 worst-case
levels. A power margin (P
M
to operate the receiver and that it does not exceed the maximum receiver input power.
This means the link will work. A (P
to operate the receiver. See the specification for your receiver to find the maximum
receiver input power.
Before you begin to calculate the power margin:
Calculate the power budget. See
a QFX Series Device" on page
To calculate the worst-case estimate for the power margin (P
Determine the maximum value for link loss (LL) by adding estimated values for
1.
applicable link-loss factors; for example, use the sample values for various factors
) and (P ) are measured in decibels, and decibels
T R
B
) by subtracting (P
) is the amount of power available after
M
) greater than zero indicates that the power budget is sufficient
) that is zero or negative indicates insufficient power
M
"Calculating the Fiber-Optic Cable Power Budget for
131.
B
) and minimum receiver
T
) from (P ):
R T
).
B
) for the link:
M
Copyright © 2017, Juniper Networks, Inc.
) for the