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Forwarding this thread onto the optics reflector From: Chris Cole <chris.cole@xxxxxxxxxxxx> Hi JJ, This is following up on the previous reflector email. If as you suggest, 802.3dj standard needs to help the novice engineer to repurpose their DR single-lane tester for FR or LR WDM measurements, then just adding an optical filter in front of the Reference Receiver does not work. i.e. it's not technically correct. We also need to include a 4:1 optical switch in the diagram to illustrate how to connect any of the four optical filter outputs to the single-lane receiver input. This is blatantly obvious, however no more so than adding a WDM DeMux to the diagram. I don't see the need to make any changes. However, if this corner case warrants a helpful illustration in the standard, we should at least do it accurately. Thank you Chris From: Chris Cole <chris.cole@xxxxxxxxxxxx> Hi JJ, I agree that a Reference Receiver is not a PMD Receive Function. However, just like with the PMD Receive Function, it is understood that Reference Receiver has appropriate wavelength selectivity. You are correct, that putting an optical filter in front of the single lane (DR) Reference receiver repurposes it for WDM testing. However, this type of helpful advice of how not to misuse test equipment does not belong in a standard. We could provide hundreds of other similarly helpful suggestions for how not shoot oneself in the foot. I also agree with you that test engineers select the correct wavelength selectivity for the Reference Receiver because it's blatantly obvious. After the meeting, I checked with multiple transceiver engineers, and everyone does the correct thing. If it's common understanding, it's blatantly obvious, and no problem exists with the existing draft why is this an issue requiring a change? If it ain't broke, don't fix it. Chris From: John Johnson <jejohnson@xxxxxxxx> Chris, I agree with you that it's unnecessary and said as much in the CRG. No test engineer worth his salt is going to omit an optical filter in front of the Reference RX used for TX testing when all TX lanes are active, but given that this is a new requirement for 200G/L optics it might surprise some that their repurposed single-lane 100G/L test setup doesn't work initially. That said, I don't agree with making an equivalence between 180.5 and 180.9. A Reference Receiver is not a PMD Receive Function, it's a piece of test hardware. For that reason, even though it ought to be blatantly obvious, showing an optical filter in front of the Reference Receiver in 181 and 183 isn't technically incorrect. Regards, John On Fri, May 15, 2026 at 1:59 AM Chris Cole <chris.cole@xxxxxxxxxxxx> wrote:
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