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*To*: STDS-802-3-10GMMF@xxxxxxxxxxxxxxxxx*Subject*: Re: [10GMMF] TP3 3-impulse test proposal*From*: "Lobel, Martin" <martin.lobel@xxxxxxxxx>*Date*: Mon, 20 Sep 2004 12:41:21 +0200*Reply-To*: "IEEE P802.3aq 10GBASE-LRM"<stds-802-3-10gmmf@xxxxxxxx>*Sender*: owner-stds-802-3-10gmmf@xxxxxxxx*Thread-Index*: AcScytPeyYPjJrFMRJOi035O/eRV1gAG8o8QAITGP9A=*Thread-Topic*: [10GMMF] TP3 3-impulse test proposal

A) From a practical implementation point of view, it makes a lot of sense to limit the number of 'taps' to a minimum (three so far). As pointed out by Lew, I'm also concerned that the limited time span of the stressor (2xdT=200 ps) will not be a good emulation of real life channel impulse responses even that the PIE are alike. Many we should consider to have two tests with different dT(?). It could, e.g., be implemented with 5 taps total. B) Comments on the dynamic test: The biggest problem for real EDC solutions may not be to handle the ~KHz variation (1 KHz has been suggested) but more the problem of been able to handle the variety of channel responses and make the transition from one response 'A' to another channel response 'B' without causing errors. The question is if we can imagine that any given Cambridge channel response may be followed by any other arbitrary Cambridge Channel response due to vibration of the fiber and/or connectors. If the answer is 'no' then the suggested dynamic test of going from a state with completely pre-cursor only to a new state with completely post-cursor only may be a too stressful test that may lead to a non-desirable trade-offs for the implementation. Regards, Martin -----Original Message----- From: owner-stds-802-3-10gmmf@IEEE.ORG [mailto:owner-stds-802-3-10gmmf@IEEE.ORG] On Behalf Of Lew Aronson Sent: 17. september 2004 21:02 To: STDS-802-3-10GMMF@listserv.ieee.org Subject: Re: [10GMMF] TP3 3-impulse test proposal I think this is very close to where we want to be for the dynamic penalty test, and I see no reason why the three impulse response functions can't be aligned with those used for the static test. A number of different comments: 1) We should do this calculation (and all similar calculations) for 300m as well as 220m. 2) It is interesting to come up with 1.0 UI for the dT. In a way that is good in that I know that many consider that a pretty demanding case, so if it makes sense with the fiber model and EDC makers consider it realistic to pass, than on that basis it might be a good choice. 3) I am concerned about deriving the details of the impulse response parameters solely from PIE metrics. The reason is that PIE is for an infinite ideal equalizer. As such, it's sensitivity to the total time span of the impulse response is presumably a lot flatter (and more non-monotonic) than is the performance of a real finite equalizer. I think we see this in that the final choice in the values was not terribly sensitivie to dT and was chosen to get a close fit on the PIE value for the -D and -L cases simulataneously. Thus, we risk coming up with a choice which is too short (compared to actual fiber response) to adequately stress a real implementation, or vice versa. Even worse, our choice is likely to drive the design tradeoffs of the EDC's used and thus should really match the dT spands from the fiber models. I would suggest that, at least in the case of the dT choice, that the fiber models and Petre's work be used to determine the approximate choice, and that we live with a larger difference in PIE-L and PIE-D that results. 4) With that said, I think the idea of having the same dT and the pre-cursor and post cursor symmetric to each other is probably a great goal for the static test as well and would then naturally align the static and dynamic tests. [This would not change my thinking on the fact that the static and dynamic tests should be seperate, I would still have many reasons to want that]. Petre's work so far has emphasized the goodness of fit to particular fiber examples. In the end, I think we just want to have something of the same general shape chosen to represent the 99% point by a combination of PIE value and represnetative dT values, and to use that extra freedom to have equal dT's between pulses and cases if at all possible. Thus, I would say that we want to wind up with something of the form Ben has given us, but with the dT and perhaps a value motivated more by Petre's work than by the most exact fit to PIE numbers. Lew Lew Aronson (lew.aronson@finisar.com) Finisar Corporation 1308 Moffett Park Drive Sunnyvale, CA 94089-1133 408-542-4215 (PH) 408-543-0083 (FAX) -----Original Message----- From: Ben Willcocks [mailto:ben.willcocks@PHYWORKS-IC.COM] Sent: Friday, September 17, 2004 8:13 AM To: STDS-802-3-10GMMF@listserv.ieee.org Subject: [10GMMF] TP3 3-impulse test proposal Further to the preliminary data I presented in the phone conference of 7 September, I have attached slides showing our TP3 3-impulse test proposal & simulation results. Many thanks to Sudeep Bhoja for his assistance regarding the PIE calculations. With Mike's permission, I would like to talk through this during next Tuesday's TP3 conference call. Regards, Ben

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