Installation guide

4-102 Cisco 4000 Series Installation Guide
Network Connection Considerations
Multimode Power Budget Example
The following is an example multimode power budget, based on the following variables,
and calculated to ensure sufficient power for transmission:
Length of multimode link = 3 kilometers (km)
4 connectors
3 splices
Higher order loss (HOL)
Clock recovery module (CRM)
Estimate the power budget as follows:
PB = 11.5 dB – 3 km (1.0 dB/km) – 4 (0.5 dB) – 3 (0.5 dB) – 0.5 dB (HOL) – 1 dB
(CRM)
PB = 11.5 dB – 3 dB – 2 dB – 1.5 dB – 0.5 dB – 1 dB
PB = 2.5 dB
The value of 2.5 dB indicates that this link would have sufficient power for transmission.
Multimode Power Budget Example of Dispersion Limit
Following is an example with the same parameters as the previous example, but with a
multimode link distance of 4 km:
PB = 11.5 dB – 4 km (1.0 dB/km) – 4 (0.5 dB) – 3 (0.5 dB) – 0.5 dB (HOL) – 1 dB
(CRM)
PB = 11.5 dB – 4 dB – 2 dB – 1.5 dB – 0.5 dB – 1 dB
PB = 1.5 dB
The value of 1.5 dB indicates that this link would have sufficient power for transmission.
But, due to the dispersion limit on the link (4 km x 155.52 MHz > 500 MHz/km), this link
would not work with multimode fiber. In this case, single-mode fiber would be the better
choice.