Re: [10GMMF] Dynamic test (was: TP3 3-impulse test proposa)l
Jonathan and all,
---"Ben Willcocks which suggests that we should use a dynamic test that shifts from post-cursor to pre-cursor at 1 KHz. I believe that this is not reproducing any real-life scenario and could be too stressful to the EDC solution."--
I think, that the suggestion of Ben Willcoocks is not to exotic. As an example: we have a standard fiber in the lab (900MHz*km) which shifts strongly from pre-cursor to post-cursor by changing the offset launch from 17µm to 23µm, just the range of the offset patchcord. You can introduce pulse changes in the transmission with a change of the input polarization. Such changes can be done fast e.g. by movement or twisting of the fiber.
In certain situations a movement of some cm will introduce this changes. Maybe the speed is not in the kHz range but 100Hz seems reasonable to me.
Joerg
Infineon Technologies
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-----Original Message-----
From: owner-stds-802-3-10gmmf@IEEE.ORG [mailto:owner-stds-802-3-10gmmf@IEEE.ORG] On Behalf Of Lobel, Martin
Sent: Dienstag, 21. September 2004 09:57
To: STDS-802-3-10GMMF@listserv.ieee.org
Subject: Re: [10GMMF] Dynamic test (was: TP3 3-impulse test proposa)l
Jonathan,
I fully agree with your observations from the lab (moving the fiber several centimeters etc.) and the fact that building vibrations will only lead to minor movements of fiber.
My comments are, however, a reflection of slide 11 of the TP3 presentation sent out on the reflector on Sep. 17th by Ben Willcocks which suggests that we should use a dynamic test that shifts from post-cursor to pre-cursor at 1 KHz. I believe that this is not reproducing any real-life scenario and could be too stressful to the EDC solution.
For a given installed fiber, I believe that two things can happen to the fiber/connector in a link:
1) The fiber undergoes vibrations due to building movements.
2) The fiber is moved (bend or twisted) by personnel during installation of other hardware, daily cleaning etc.
My comment is related to 2) which can cause (in line with your observations in the lab) large changes in the channel impulse response. I don't know the nature of such changes but believe they can be large but with a longer time scale than vibrations (how fast can you move a fiber by hand). I believe that it is vital to study these nature of such large changes and ensure that any dynamic test covers the 2) case.
I'm looking forward to the report out from the Task 2 to understand more about the physical behavior of the channel.
Thanks,
Martin
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Martin Lobel, M.Sc.E.E., Ph.D.
Standards and Advanced Technology
Intel Copenhagen ApS
Mileparken 22
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Denmark
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-----Original Message-----
From: owner-stds-802-3-10gmmf@IEEE.ORG [mailto:owner-stds-802-3-10gmmf@IEEE.ORG] On Behalf Of Jonathan King
Sent: 21. september 2004 01:48
To: STDS-802-3-10GMMF@listserv.ieee.org
Subject: Re: [10GMMF] TP3 3-impulse test proposal
Hi Martin
I have a comment on the TP3 dynamic response test.
I expect that the TP3 dynamic test will need to be significantly below 1kHz rate if it is to be realistic.
Task 2 is actively studying time variation effects, and is basing tests on GR-63-CORE which is an existing standard describing appropriate operational testing for in building environments. It describes vibration testing from 5Hz to 100Hz, with constant acceleration stimulus (0.1g and 1g accelerations). For constant acceleration, the amplitude of vibration decreases with the square of the frequency, for example:
At 5Hz and 1g acceleration, vibration amplitude is 2 cm peak to peak, comparable to a rather fast fibre shaker as described in TIA/EIA-455-203; At 50Hz and 1g acceleration, vibration amplitude is 0.2 millimetres peak to peak; At 500Hz and 1g acceleration, vibration amplitude is 2 microns peak to peak;
I think its common experience in the laboratory that large changes in IPR occur only when a fibre coil is distorted by several centimetres, with relatively insignificant changes in IPR at displacements much below 1mm. I expect this will place an upper bound on the test frequency in the ~10Hz range
best wishes
Jonathan
tel: 1 408 524 5110
e-mail: jking@bigbearnetworks.com
fax: 1 408 739 0568
Jonathan King
Director, Optical Systems
BigBear Networks
345 Potrero Avenue
Sunnyvale, CA 94085
-----Original Message-----
From: Lobel, Martin [mailto:martin.lobel@INTEL.COM]
Sent: Monday, September 20, 2004 3:47 AM
To: STDS-802-3-10GMMF@listserv.ieee.org
Subject: Re: [10GMMF] TP3 3-impulse test proposal
All,
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