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Fibre-Optic Transmission Specifications
The following equation lists the calculation of the power budget:
PB = PT – PR
The SONET specification requires that the signal meet the worst case parameters listed in
Table 1-6
Value
PT
PR
PB
In the following example of a single-mode power budget, two buildings, 8 kilometers apart, are
connected through a patch panel in an intervening building with a total of 12 connectors.
Length of single-mode link = 8 km
12 connectors
The power margin is equal to the PB value minus the link loss:
PM = PB – LL
PM = 16 dB – 8 km (0.5 dB/km) – 12 (0.5 dB)
PM = 16 dB – 4 dB – 6 dB
PM = 6 dB
The value of 6 dB indicates that this link has sufficient power for transmission and does not exceed the
maximum receiver input power.
If the power margin is positive, as a rule, the link will work.
Table 1-7
to each factor.
Table 1-7
Link Loss Factor
Higher order mode losses
Clock recovery module
Modal and chromatic dispersion
Connector
Splice
Fibre attenuation
The power margin (calculated above) should be greater than zero. Circuits whose results are less than
zero may have insufficient power to operate the receiver.
PA-A2 ATM CES Port Adapter Installation and Configuration
1-22
PA-A2 ATM CES Port Adapter SONET Signal Requirements
Single-Mode Signal
-15 dBm
-31 dBm
-16 dBm
lists the factors that contribute to link loss and the estimate of the link loss value attributable
Typical Link Loss Factors and Values
Chapter 1
Overview: PA-A2 ATM CES Port Adapter
Estimate of Link Loss Value
0.5 dB
1 dB
Dependent on fibre and wavelength used
0.5 dB
0.5 dB
1 dB/km
Table
1-6.
OL-3460-01
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