Calculate The Fiber-Optic Cable Power Budget For Ex Series Devices; Calculating The Fiber-Optic Cable Power Margin For Ex Series Devices - Juniper EX9214 Hardware Manual

Calculate the Fiber-Optic Cable Power Budget for EX Series Devices

To ensure that fiber-optic connections have sufficient power for correct operation, calculate the link's
power budget when planning fiber-optic cable layout and distances. This planning helps you 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. You use a worst-case analysis even though not all the parts of an
actual system operate at the worst-case levels.
To calculate the worst-case estimate for a fiber-optic cable power budget (
1. Determine values for the link's minimum transmitter power (
P
( ). In the following example, we measure both (
R
(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.
2. Calculate the power budget (
– 15 dBm – (–28 dBm) = 13 dBm

Calculating the Fiber-Optic Cable Power Margin for EX Series Devices

Before calculating the power margin, calculate the power budget (see
Power Budget for EX Series Devices
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 loss and still satisfy the
minimum input requirements of the receiver for the required performance level. The power margin (
is the amount of power available after you subtract attenuation or link loss (
P
( ).
B
When you calculate the power margin, you use a worst-case analysis to provide a margin of error, even
though not all parts of an actual system operate at worst-case levels. A power margin (
zero indicates that the power budget is sufficient to operate the receiver and that it does not exceed the
maximum receiver input power. This means that the link will work. A (
P
) and (
T
P P
) by subtracting ( ) from (
B R
).
P
) for the link:
B
P
) and minimum receiver sensitivity
T
P
) in decibels relative to one milliwatt
R
P
):
T
Calculating the Fiber-Optic Cable
LL ) from the power budget
P
) that is zero or negative
M
140
P
)
M
P ) greater than
M