Table 40: Estimated Values For Factors Causing Link Loss - Juniper SRX 5600 Hardware Manual

P
P
P
Calculating Power Margin for Fiber-Optic Cable
After calculating a link's power budget (using the equation described in "Calculating
Power Budget for Fiber-Optic Cable" on page 198), you can calculate the power margin
(
or link loss (
maximum
P
A
receiver.
Factors that can cause link loss include higher-order mode losses, modal and
chromatic dispersion, connectors, splices, and fiber attenuation. Table 40 on page
199 lists an estimated amount of loss for the factors used in the following sample
calculations. For information about the actual amount of signal loss caused by
equipment and other factors, refer to vendor documentation.

Table 40: Estimated Values for Factors Causing Link Loss

The following example uses the estimated values in Table 40 on page 199 to calculate
link loss (
= P P
B T R
= 15 dBm ( 28 dBm)
B
= 13 dB
B
P ), which represents the amount of power available after subtracting attenuation
M
) from the power budget (
LL
LL :
= P LL
M B
greater than zero indicates that the power budget is sufficient to operate the
P
M
Link-Loss Factor
Higher-order mode losses
Modal and chromatic dispersion
Connector
Splice
Fiber attenuation
) for a 2 km-long multimode link with a power budget (
LL
Fiber attenuation for 2 km @ 1.0 dB/km= 2 dB
Loss for five connectors @ 0.5 dB per connector = 5(0.5 dB) = 2.5 dB
Loss for two splices @ 0.5 dB per splice =2(0.5 dB) = 1 dB
Appendix E: Cable and Wire Guidelines and Specifications
). A worst-case estimate of
P
B
Estimated Link-Loss Value
Single-mode—None
Multimode—0.5 dB
Single-mode—None
Multimode—None, if product of bandwidth and distance
is less than 500 MHz–km
0.5 dB
0.5 dB
Single-mode—0.5 dB/km
Multimode—1 dB/km
Network Cable Specifications and Guidelines
assumes
P
M
) of 13 dB:
P
B
199