Sent: Wednesday, May 20, 2026 3:09 AM
To: Chris Cole <chris.cole@xxxxxxxxxxxx>; STDS-802-3-B400G-OPTX@xxxxxxxxxxxxxxxxx <STDS-802-3-B400G-OPTX@xxxxxxxxxxxxxxxxx>
Subject: [EXTERNAL]: RE: [802.3_B400G_OPTX] FW: [802.3_B400G] WDM Transceiver functionality
I submitted the comment and the suggested remedy is based on the existing TDECQ setup in clause 122.
The same test setup is referenced in 151.8.5.
An optical filter is also mentioned in the text of 87.8.6.4 and 88.8.5.4: “each lane is tested individually using an optical filter to separate the lane under test from the others”.
An optical filter is also mentioned in the text of 53.9.10.1 and in Figure 53–9.
So it seems that all previous WDM clauses explicitly call for an optical filter – there is sufficient precedence.
There may be other ways to build a test setup but this is the reference setup, and being consistent with the base standard should not create a problem for any test engineer, novice or seasoned.
If this diagram or the concept of using an optical filter is incorrect, it can be dealt with by a comment against D3.1 or in the upcoming revision project (which will also include 802.3dj if we finish it on time). Let’s not argue about it over the reflector.
</Adee>
From: Chris Cole <chris.cole@xxxxxxxxxxxx>
Sent: Wednesday, May 20, 2026 11:32 AM
To: STDS-802-3-B400G-OPTX@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_B400G_OPTX] FW: [802.3_B400G] WDM Transceiver functionality
Hi Kent,
Yes, I meant that I am unaware of anyone using a tunable filter in testing individual wavelengths of FR and LR optics. I had asked multiple individuals affiliated with transceiver vendors, and they all confirmed that they use a fixed WDM DeMux.
Chris
From: Kent Lusted <Kent.Lusted@xxxxxxxxxxxx>
Sent: Tuesday, May 19, 2026 11:47 PM
To: Chris Cole <chris.cole@xxxxxxxxxxxx>;
STDS-802-3-B400G-OPTX@xxxxxxxxxxxxxxxxx <STDS-802-3-B400G-OPTX@xxxxxxxxxxxxxxxxx>
Subject: RE: [802.3_B400G_OPTX] FW: [802.3_B400G] WDM Transceiver functionality
Hi, Chris,
The use of the term “nobody” is not quantifiable. Do I understand that your intent was to the effect of “I am not aware of anyone who uses…”
-Kent
From: Chris Cole <chris.cole@xxxxxxxxxxxx>
Sent: Tuesday, May 19, 2026 6:58 PM
To: STDS-802-3-B400G-OPTX@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_B400G_OPTX] FW: [802.3_B400G] WDM Transceiver functionality
JJ
Nobody uses tunable filters for this test. The suggestion to do so is impractical, and if the objective is to steer novice engineers in the right direction, this would be going in the opposite direction.
What is done is to use a WDM DeMux, followed by a switch which selects one of the outputs, or it's done manually, i.e. the engineer performs the function of a switch. No definition of an optical filter includes a switch. This is always considered a separate device.
However, a switching function can be part of a Reference Receiver as part of wavelength selection. That's why what's in the draft today is technically correct, and adding an optical filter in front of the Reference Receiver is technical insufficient.
Chris
From: John Johnson <jejohnson@xxxxxxxx>
Sent: Tuesday, May 19, 2026 7:20 AM
To: STDS-802-3-B400G-OPTX@xxxxxxxxxxxxxxxxx <STDS-802-3-B400G-OPTX@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_B400G_OPTX] FW: [802.3_B400G] WDM Transceiver functionality
Hi Chris,
A demux and optical switch is one possible implementation, but this function can also be achieved with e.g. a tunable optical filter or other means. Specifying the use of a generic "Optical Filter" element in front of the Ref Rx is sufficient without limiting any particular implementations. I agree this is all very obvious, but comment #95 was accepted by consensus of the CRG.
Regards,
John
On Tue, May 19, 2026 at 9:46 AM John D'Ambrosia <jdambrosia@xxxxxxxxx> wrote:
Forwarding this thread onto the optics reflector
From: Chris Cole <chris.cole@xxxxxxxxxxxx>
Sent: Tuesday, May 19, 2026 4:57 AM
To: STDS-802-3-B400G@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_B400G] WDM Transceiver functionality
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>
Sent: Monday, May 18, 2026 1:27 PM
To: STDS-802-3-B400G@xxxxxxxxxxxxxxxxx <STDS-802-3-B400G@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_B400G] WDM Transceiver functionality
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>
Sent: Monday, May 18, 2026 7:35 AM
To: STDS-802-3-B400G@xxxxxxxxxxxxxxxxx <STDS-802-3-B400G@xxxxxxxxxxxxxxxxx>
Subject: [EXTERNAL]: Re: [802.3_B400G] WDM Transceiver functionality
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:
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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