Installation guide

Making External Connections to Cisco 4000 Series Routers 4-101
Network Connection Considerations
The power margin calculation is derived from the power budget and subtracts the link loss,
as follows:
M = PB – LL
If the power margin is positive, as a rule, the link will work.
Table 4-12 lists the factors that contribute to link loss and the estimate of the link loss value
attributable to those factors.
After calculating the power budget minus the data link loss, the result should be greater than
zero. Results less than zero may have insufficient power to operate the receiver.
For SONET versions of the ATM module, the signal must meet the worst-case parameters
listed in Table 4-13.
Table 4-12 Estimating Link Loss
Table 4-13 SONET Signal Requirements
Link Loss Factor Estimate of Link Loss Value
Higher order mode losses 0.5 dB
Clock recovery module 1 dB
Modal and chromatic dispersion Dependent on fiber and wavelength used
Connector 0.5 dB
Splice 0.5 dB
Fiber attenuation 1 dB/km
Signal Single-Mode Multimode
T –18.5 –15
PR –30 –28
PB –11.5 –13