Juniper CBL-M40-PWR-AU Manuel D’Utilisation
Prepare the Site
Fiber-Optic and Network Cable Guidelines
51
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. For more information calculating the power budget, see
“Power Budget Calculation” on page 51.
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. For more information calculating the power budget, see
“Power Budget Calculation” on page 51.
Power Budget Calculation
A link’s power budget is the maximum amount of power it 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 of power budget (
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 of power budget (
P
B
), you assume minimum transmitter power (
P
T
) and
minimum receiver sensitivity (
P
R
).
Table 15 lists equations for calculating the power budget for SONET/SDH PIC interfaces. The
values are measured in decibels (dB) and decibels referred to one milliwatt (dBm).
values are measured in decibels (dB) and decibels referred to one milliwatt (dBm).
Table 15: Calculating Power Budget for SONET/SDH PIC Interfaces
Power Margin Calculation
After calculating a link’s power budget (using the equation described in “Power Budget
Calculation” on page 51), you can calculate the power margin (
Calculation” on page 51), you can calculate the power margin (
P
M
), which estimates the
amount of power available after subtracting attenuation or link loss (
LL
) from the power
budget (
P
B
). A worst-case estimate of
P
M
assumes maximum
LL
:
P
M
= P
B
– LL
A
P
M
greater than zero indicates that the power budget is sufficient to operate the receiver.
PIC Interface
Power Budget Equation
Multimode
P
B
= P
T
– P
R
P
B
= –15 dBm – (–28 dBm)
P
B
= 13 dB
OC-12 single-mode P
B
= P
T
– P
R
P
B
= –15 dBm – (–28 dBm)
P
B
= 13 dB
OC-48 single-mode P
B
= P
T
– P
R
P
B
= –5 dBm – (–18 dBm)
P
B
= 13 dB