With [D]WDM systems the data path might not be measurable; e.g. if you have multiple 10Gbps grey light from edge devices coming in these are then converted into colored light before being optically multiplexed onto a single piece of glass, and at no point did you actually have an Ethernet frame.
You're more likely to get something useful form traps from these types of devices (we have Cisco ONS and Infinera WDM devices)
