Cisco Cisco DWDM Transceiver Modules White Paper

 

 

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Figure 2.    Interference Occurring When Monitoring QSFP BiDi Transmissions 

 

Note that the passive BiDi optical tap is different from the one in Figure 2. The passive BiDi optical tap must pull 

the signals of both directions from each fiber. 

Bidirectional Network Monitoring 

To solve the BiDi tap issue, a 

“BiDi monitor” transceiver is used in the monitor ports. Since the monitor hardware 

requires only the receive signal for its processing and analysis, the transmit signal is expendable. What if we 

remove the transmitter (or laser) of the bidirectional transceiver for tapping? There is then no transmitted signal to 

interfere with the live link. Hence, the Cisco QSFP BiDi Monitor is a QSFP BiDi transceiver with the transmitters 

removed. This solution is shown in Figure 3. 

Figure 3.    Cisco QSFP BiDi Monitor