Calculating The Ex Series Switch Fiber-Optic Cable Power Margin - Juniper EX4300 Hardware Manual

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Calculating the EX Series Switch Fiber-Optic Cable Power Margin

Copyright © 2015, Juniper Networks, Inc.
To calculate the worst-case estimate for 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
decibels are referred to one 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
Calculating the EX Series Switch Fiber-Optic Cable Power Margin on page 103
Understanding EX Series Switches Fiber-Optic Cable Signal Loss, Attenuation, and
Dispersion on page 137
Pluggable Transceivers Supported on EX Series Switches
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
Power Budget" 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
Chapter 7: Power Specifications and Requirements
) and (P ) are measured in decibels, and
T R
) by subtracting (P
B
) 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 EX Series Switch Fiber-Optic Cable
102.
) for the
B
) and minimum receiver
T
) from (P ):
R T
).
B
) for the link:
M
103