Testing The Physical Interface


100G testing plans must include specific attention to the physical interface. The CFP interface is no longer a single transmitter and receiver pair that can simply be checked with simple tests such as a basic optical power measurement or receiver sensitivity measurement.

Utilising multiple optical lanes simultaneously makes testing the interface more complex and also testing the associate alarm conditions and reporting will be more in depth. In the case where there is a loss of signal (LOS) condition on one of the lanes of the CFP interface it must be understood how that condition will be detected, reported and diagnosed. In some cases a network element or test set will not be able to measure the optical power or LOS condition on an individual lane.

Consider the case of a power reduction or LOS on a single lane – this event might not be easily identifiable. If the device under test does not recognise and report individual lane alarms it could simply report a loss of Ethernet link on an Ethernet network or OTU & OTL layer alarms on an OTN network. In this case it would not be possible to diagnose the root cause of the fault purely from the alarm reporting functions of the network element and so it would be necessary to deploy a test set to diagnose the fault.

It would essential that any 100G test set that was used would be able to measure the optical parameters including the TX & RX power levels across all lanes individually. Simply reporting a total power level across the interface absolutely does not provide the level of reporting to diagnose faults on these multi-lane interfaces at the 100Gb/s rate.