Cisco CAB-232MT= Fiche technique télécharger pdf (Page 24)

C-24

Cisco 7100 Series VPN Router Installation and Configuration Guide

78-6341-03

Appendix C Cable Specifications

Cisco 7120-AT3, Cisco 7140-2AT3, Cisco 7120-AE3, Cisco 7140-2AE3, Cisco 7120-SMI3, and Cisco 7140-2MM3 Cables

After calculating the power budget minus the data link loss, the result should be greater than zero.

Circuits whose results are less than zero may have insufficient power to operate the receiver.

The SONET specification requires that the signal must meet the worst-case parameters listed

in Table C-23.

Multimode Power Budget Example with Sufficient Power for Transmission

The following is an example multimode power budget calculated based on the following variables:

• Length of multimode link = 3 kilometers (km)

• Four connectors

• Three splices

• Higher-order mode loss (HOL)

• Clock recovery module (CRM)

Estimate the power budget as follows:

PB = 10 dB – 3 km (1.0 dB/km) – 4 (0.5 dB) – 3 (0.5 dB) – 0.5 dB (HOL) – 1 dB (CRM)

PB = 10 dB – 3 dB – 2 dB – 1.5 dB – 0.5 dB – 1 dB

PB = 2 dB

The positive value of 2 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 = 10 dB – 4 km (1.0 dB/km) – 4 (0.5 dB) – 3 (0.5 dB) – 0.5 dB (HOL) – 1 dB (CRM)

PB = 10 dB – 4 dB – 2 dB – 1.5 dB – 0.5 dB – 1 dB

PB = 1 dB

The value of 1 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.

Splice 0.5 dB

Fiber attenuation 1 dB/km

Table C-22 Link Loss Factors and Values (continued)

Link Loss Factor Estimate of Link Loss Value

Table C-23 MM3 and SMI3 Port SONET Signal Requirements

Variable Single Mode (SML) Single Mode (SMI) Multimode

PT –5 dBm –15 dBm –20 dBm

PR –34 dBm –31 dBm –30 dBm

PB 29 dBm 16 dB 10 dB

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Cisco CAB-232MT= Fiche technique Page 24