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Dear Group I do want to add to Ruben’s comment a few more items. You can find my comments weaved in below mail. I also want to add a reference to a recent paper by HPE impressively describing the properties of long wavelength VCSELs:
https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=9036953 Best regards Phone: +49 731 550194-0, Mobile: +49 171 3361262,
joseph.pankert@xxxxxxxxxx De: Richard Pitwon <rcapitwon@xxxxxxxx> Asunto: Re: [802.3_OMEGA] Motion #3 for PMD adoption. Understanding the negative votes. Fecha: 26 de octubre de 2021, 13:55:22 CEST Para: Rubén Pérez-Aranda <rubenpda@xxxxxxxxx> Cc: STDS-802-3-OMEGA@xxxxxxxxxxxxxxxxx Dear Ruben, I'm afraid I cannot attend this afternoon's meeting due to a plenary, but I just wanted to underline for the TF my concerns as I've expressed to the group and to you privately in our correspondence over the last few months
and why I must maintain that 980nm + OM3 has not been shown to meet the Technical Feasibility CSD. Reply J. Pankert: I do have an issue with the logics of this procedure. 980nm has provided best data when compared to 850nm solutions, and certainly compared
to SiP solution for which we have not seen data on long-term reliability at all. Standardization is meant to guide the product development, not to finally qualify products. The 980nm solution will be a working solution and we have not seen a better alternative
in the OMEGA working group. This automotive application is not like most applications in IEEE 802.3 in that the technology we choose will directly affect the safety of billions of people. This is not an exaggeration. There are a billion cars
in the world today. If even 20% of those adopt internal optical communication systems, billions of people will be dependent on these optical "nerves" between the safety critical sensors around the car, on which automotive is becoming more and more dependent,
and the onboard computer where sensor input is processed and reactions executed. These optical links will therefore be critical to the safety of cars and their billions of passengers in the coming years. Reply J. Pankert: Why would this discriminate optical against any other potential solution? Any electronics component has a potential to fail. Safety must
be guaranteed on system level which involves multiple layers and does not rely on single component/connector/solder-bump.. failures. VCSELs are used today in many aerospace applications with requirements at least as stringent as for the automotive industry. The most serious cause of failure in VCSELs operating beyond 100 degrees, while being directly modulated is random failure, in particular due to so called "dark line defects" or "etch point defects". As per Joseph's contribution in June (https://www.ieee802.org/3/cz/public/22_jun_2021/pankert_3cz_01_220621_random_failures.pdf),
while the density of defects in 850nm, 940nm and 980 nm has decreased to 100 / cm2, any one of those defects can propagate given the right conditions and cause a sudden failure. The risk of defect propagation and the resulting random failure increases exponentially
as we approach and exceed 100 degrees and the risk is further strongly compounded by direct modulation i.e. turning the laser on and off rapidly. This is analogous to standing on a plane of glass compared to jumping up and down on a plane of glass. Therefore
the risk of random failure is much more severe under automotive conditions and needs to be addressed. Reply J.Pankert:
However, in spite of random failure being the most serious potential cause of 980nm VCSEL failure in the target environment, there has been no experimental, statistical or otherwise empirical evaluation in this TF of
the actual risk of random failure on 980nm VCSELs under these extreme automotive conditions. We still have no idea whether it would be 0.1%, 1%, 10% or 25% (none of which would be acceptable of course) or indeed 0%. Reply J. Pankert: Would anyone can provide such data for 850nm or SiP? The point is that such data only can be generated when a large number have been
manufactured and have undergone the rigorous automotive qualification process. This will not happen if there is no consensus about a standard (automotive tier 1 simply will not take the effort). My concern is that most of the contributions on 980 nm VCSELs have focussed on other "safer" areas such as the lower risk of wear-out failure, which is a different mechanism and, for post-burn-in VCSELs, not expected
to be high. As stated in Joseph's contributions, while wear-out failure is much lower in 980 nm VCSELs compared to 850nm VCSELs, the occurrence of these etch point defects is exactly the same for 850nm, 940nm and
980nm VCSELs. In addition to this we mustn't forget that 980nm VCSELs are largely unproven for transceiver applications. Any TF member can carry out their own quick litmus on the general availability of 980nm transceivers by simply
googling "980 nm transceiver". I still found nothing apart from pump lasers, but someone mentioned that they exist so I will assume that this is the case. Reply J. Pankert: By far the biggest data set is available from the 940nm devices that are used in billions of phones, each with >300 VCSEL channels. 940nm
and 980nm are very comparable. VCSEL solutions in optical interconnects are around for 20 years and we know very well the potential and the limits of the technology. 980nm is adding to today’s space the higher operating temperature, but otherwise with no draw-back.
As I've assured you before, I am not seeking to exclude VCSELs, I have worked with VCSELs for over 20 years, it's a technology I trust for data centres, but you cannot claim to meet Technical Feasibility when you have
not addressed the greatest cause of failure in the target environment i.e. random failure. If our roles were reversed I think you would not accept the same from me (and of course you'd be right not to). I hope you'll agree that this is a serious matter and I hope that it can be discussed without contention going forward. Kind regards Richard Pitwon On Thu, Oct 14, 2021 at 7:59 PM Rubén Pérez-Aranda <rubenpda@xxxxxxxxx> wrote: Dear Colleagues, Related with the technical opinion expressed below, I would like to emphasize a comment that Kjersti Martino already did in our last meetings. She commented that the -40ºC performance is a problem for 850nm VCSELs because once the 850nm VCSEL is adjusted to try to meet performance requirements at 125ºC, its performance at -40ºC is compromised. This comment is consistent with my observation in the lab experiments, and it should not be ignored. Fortunately, I already reported data in several contributions that support this comment. https://www.ieee802.org/3/cz/public/11_may_2021/perezaranda_3cz_01a_110521_50Gbps_850nm_demo.pdf :
https://www.ieee802.org/3/cz/public/may_2021/perezaranda_3cz_01_0521_VCSEL_980nm.pdf :
Thank you and best regards, Rubén Pérez-Aranda KDPOF El 13 oct 2021, a las 23:55, Rubén Pérez-Aranda <rubenpda@xxxxxxxxx> escribió: Dear Colleagues, I have received a reason behind one negative vote: "I would like to see 850nm wavelengths included in the PMD, per Ramana’s proposal.” I appreciate the feedback. Please, send the responses to the reflector, so we can use it for consensus building in a common discussion. Next I am going to elaborate my technical opinion about including 850nm in the PMD:
I am sorry for the long response, but wavelength is not an easy topic in this project. There are a lot of arguments that we, the proponents of PMD based on OM3 + 980nm VCSEL, have considered. I hope you appreciate the effort to put all this information together; I did it to make easier to follow arguments and relevant contributions. Thank you and best regards, Rubén Pérez-Aranda KDPOF El 12 oct 2021, a las 23:13, Rubén Pérez-Aranda <rubenpda@xxxxxxxxx> escribió: Dear Colleagues, Today, in the 802.3cz Interim Meeting we have succeeded in the adoption of 4 baseline proposals (i.e. 50G PCS/PMA, EEE/LPI, Loopback modes, and BER test mode). However, the most important motion, the one to adopt a PMD failed and most of the negative voters did not provide any reason for explaining their vote, and what for me is more important, they did not indicate what should be changed in that PMD baseline proposal to be accepted by them. Today we voted the only one PMD proposal presented until now that is technically complete, fulfills the 100% of the objectives and is 100% consistent with the CSD responses. The other PMD proposals (i.e. GIPOF and Si-Photonics) are not technically complete (at least today), and either do not fulfill none of the objectives or only some of them. I understand that someone can vote against option “A”, when he/she offers an option “B”, being both A and B complete and consistent with the objectives and CSD. However, I can't understand a negative vote against option A with nothing to offer (at least today) and with no arguments. Which part of the motion text and referenced contributions should be changed, with proposed remedy, in order the motion being accepted? Should the PMD based on OM3 + 980nm VCSEL not be included in 802.3cz draft and the task force should wait until other PMD options are complete and meet (new) objectives? Why (technical reason)? Should we have also included the other PMD options in the motion, even if they are incomplete and inconsistent with objectives, going against CSD? Did the motion text or the referenced contribution prevent the adoption of future PMD options like GIPOF and Si-Photonics (provided the objectives and CSD are revised first)? Therefore, I kindly ask the following individuals to provide arguments for supporting their negative vote against the motion #3 for PMD adoption of today. These arguments may be used to identify gaps in understanding the procedures and building consensus in the future.
Thank you and best regards, Rubén Pérez-Aranda KDPOF To unsubscribe from the STDS-802-3-OMEGA list, click the following link:https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-OMEGA&A=1 To unsubscribe from the STDS-802-3-OMEGA list, click the following link:https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-OMEGA&A=1 To unsubscribe from the STDS-802-3-OMEGA list, click the following link:https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-OMEGA&A=1 To unsubscribe from the STDS-802-3-OMEGA list, click the following link:
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