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Dear 802.3dj TF Pariticipants,
During Thursday's comment #95 resolution, there was some confusion about WDM transceiver (transmitter and receiver) functionality, so clarification may be helpful.
Common usage of a datacom WDM transceiver includes appropriate wavelength selective functionality. All 802.3 WDM optics are implemented as transceiver modules, and those contain WDM Mux and DeMux functionality in the transmitter and receiver portion, including
block diagrams.
A widespread example is mobile devices. Their RF transceivers, including 802.11 ones, are understood to contain frequency selective functionality. This functionality cannot even be separated from the rest of the transmit and receive functionality, including
in block diagrams.
This has always been the usage in 802.3 WDM optics. Most recently, 181.5.3 and 183.5.3 state “the PMD Receive function shall demultiplex the composite optical signal received from the MDI into four separate optical signals. The four optical signals shall
then be converted into four symbol streams for delivery to the PMD service interface.” In contrast,
180.5.3 and 182.5.3 state "The PMD Receive function shall convert the n parallel optical signals received from the MDI into separate symbol streams for delivery to the PMD service interface."
Therefore, in Table 190-9, TDECQ conformance test diagram, the Reference receiver block contains the appropriate wavelength selective functionality. For
181 and 183 that’s WDM DeMuxing, and for 180 and 182 that’s none. Adding an optical filter block before the Reference receiver block in 181 and 183 is unnecessary and technically incorrect.
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