Calculating The Fiber-Optic Cable Power Budget For Ex Series Devices; Calculating The Fiber-Optic Cable Power Margin For Ex Series Devices - Juniper EX2300 Series Hardware Manual

Calculating 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 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 (
1. Determine values for the link's minimum transmitter power (
P
( ). For example, here, (
R
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.
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
Devices" on page 81).
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 (
is the amount of power available after attenuation or link loss (
P
budget ( ).
B
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 (
greater than zero indicates that the power budget is sufficient to operate the receiver and that it does
P P
) and ( ) are measured in decibels, and decibels are referred to one
T R
P P
) by subtracting (
B
"Calculating the Fiber-Optic Cable Power Budget for EX Series
P
) for the link:
B
P
) and minimum receiver sensitivity
T
P
) from ( ):
R T
LL ) has been subtracted from the power
81
P
)
M
P
)
M