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Dear 802.3dj Task Force Participants,
Since the proposal of TFT at the July meeting last year, a persistent concern and subject of multiple comments have been the use of a hardware optical receiver (ORx) for the functional receiver (FnRx), instead of a hardware Golden Receiver (GnRx), resulting
in TFT variability or failure.
A GnRx is a fully specified receiver, including such characteristics as noise density, signal bandwidth, and jitter-tracking bandwidth. It is difficult to specify, build, and is not practical or cost effective. That's why for TECQ and TDECQ we specify a scope-based
software receiver, and for TFT we specify an ORx.
If FnRx was just an ORx, i.e.
Set-up 1: DUT Tx => ORx1
Set-up 2: DUT Tx => ORx2
then the persistent concerns would be valid. ORx differences would result in differences in TFT results.
However, the FnRx is not just an ORx, but an ORx that is preceded by a VOA:
Set-up 1: DUT Tx => GnRx
Set-up 2: DUT Tx => VOA => ORx
The breakthrough during the TF discussion yesterday was realization that there is a VOA setting in Set-up 2 which enables approximating GnRx in Set-up 1, i.e. results in a similar error rate.
Therefore, the real issue is NOT whether TFT is correct, but whether the TFT correctly specifies the VOA setting.
Going forward, it will help advance discussion and understanding if concerns and comments are directed at the VOA setting specification. Continuing to point out that differences in ORx if not accounted for will lead to differences in TFT results, will be repeating
an obvious and agreed to understanding.
Thank you
Chris
From: Chris Cole <chris.cole@xxxxxxxxxxxx>
Dear 802.3dj Task Force Optical Track Participants,
The Transmitter Functional Test (TFT) was first proposed at the July '25 meeting [ieee802.org], with updates at every meeting since then. Other than adding test fiber to the proposal at the Sept. '25 meeting [ieee802.org], all the changes and additions are to make TFT more understandable. May '26 presentation appendices 1 and 2 [ieee802.org] are continued refinements. Yet even last week, we were addressing questions.
Because TFT presentations and specifications are not stand alone, a request was made to and received approval from the Ethernet Alliance (EA) Leadership to work on an EA White Paper fully explaining TFT. Because the objectives of the Ethernet Alliance [ethernetalliance.org] is to promote rather than develop Ethernet Technology, the technical content of the TFT White Paper will explain 802.3dj material, summarized in the May '26 presentation appendices. It is therefore important that this content continue to get close review.
During this week, little time during the official meetings can be devoted to extensive explanations of TFT. However, Optical Track Editorial Team members, as well as myself, will be available for off-line discussions to make sure that TFT explanations are fully understandable. Please ask to meet with us if there is any aspect of TFT and the May '26 presentation appendices that is not clear. This will maximize the accuracy and clarity of the EA TFT White Paper.
Thank you
Chris To unsubscribe from the STDS-802-3-B400G list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-B400G&A=1 |