How to Calculate Power Margin for Fiber-Optic Cable
After calculating a link's power budget, you can calculate the power margin (P
M
), which represents 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
P
M
greater than zero indicates that the power budget is sufficient to operate the receiver.
Factors that can cause link loss include higher-order mode losses, modal and chromatic dispersion,
connectors, splices, and fiber attenuation.
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 28: Estimated Values for Factors Causing Link Loss
Estimated Link-Loss Value
Link-Loss Factor
Single mode—None
Multimode—0.5 dB
Higher-order mode losses
Single mode—None
Multimode—None, if product of bandwidth and distance is less than
500 MHz-km
Modal and chromatic dispersion
0.5 dB
Connector
0.5 dB
Splice
Single mode—0.5 dB/km
Multimode—1 dB/km
Fiber attenuation
The following sample calculation for a 2-km-long multimode link with a power budget (P
B
) of 13 dB uses
the estimated values from
to calculate link loss (LL) as the sum of fiber attenuation
(2 km @ 1 dB/km, or 2 dB) and loss for five connectors (0.5 dB per connector, or 2.5 dB) and two splices
(0.5 dB per splice, or 1 dB) as well as higher-order mode losses (0.5 dB). The power margin (P
M
) is calculated
as follows:
P
M
= P
B
– LL
P
M
= 13 dB – 2 km (1 dB/km) – 5 (0.5 dB) – 2 (0.5 dB) – 0.5 dB
P
M
= 13 dB – 2 dB – 2.5 dB – 1 dB – 0.5 dB
82
Summary of Contents for ACX2000
Page 1: ...ACX2000 and ACX2100 Universal Metro Router Hardware Guide Published 2020 09 07 ...
Page 91: ...Front Panel of an ACX2000 Router 47 LEDs on ACX2000 and ACX2100 Routers 57 91 ...
Page 116: ...4 CHAPTER Maintaining Components Maintaining ACX2000 and ACX2100 Components 117 ...
Page 125: ...5 CHAPTER Troubleshooting Hardware Troubleshooting ACX2000 and ACX2100 126 ...
Page 139: ...139 ...
Page 144: ...Restricted Access Warning 144 ...
Page 148: ...148 ...
Page 161: ...Jewelry Removal Warning 161 ...
Page 164: ...Operating Temperature Warning 164 ...
Page 174: ...DC Power Disconnection Warning 174 ...
Page 178: ...DC Power Wiring Sequence Warning 178 ...
