| Jonathan
Lets look at sample example assuming 25.78 GBd operation for a laser with Teff=24 ps, with DCD=4.28 ps.
B= 1/(1/25.78 - DCD/1000) =28.74 GBd would be the effective bitrate
The current spreadsheet predicates if DCD (the intention here was DDPWS) increases then effective bitrate increases as expected the ISI penalty should but not the MPN and cross penalty!
What I suggest to use for B for calculation of MPN and Cross is the B1= 0.35/Teff = 14.5 GHz instead of 28.977 GHz.
If you take 10G VCSEL and operate it at 25.78 GBd, will the MPN increase? At first order the answer is no, only the ISI should increase otherwise you are double counting the penalty. When I use B1=14.5 GHz then the MPN goes from 0.4 to 0.03 dBo and Pcross goes from 5.38 to 1.69 dBo at 115 m of OM3 just before the spreadsheet blows up.
Thanks, Ali
On Feb 16, 2012, at 11:02 AM, Jonathan King wrote: Hi Ali Thanks for your e-mail - the statement to note recent work in T.11 is just that – we should take note of the work and look at what the consequences are for Ethernet rates. My understanding of the spreadsheet is that the MPN penalty is counted just once: the average effect of chromatic dispersion for a multimode source with a given rms spectral width is included in the ISI penalty; the MPN term just accounts for the noise term due to power moving around between laser modes. Can you explain what you mean by double counting ? Thanks jonathan From: Ali Ghiasi [mailto:aghiasi@xxxxxxxxxxxx]
Sent: Thursday, February 16, 2012 9:58 AM
To: Jonathan King
Cc: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_100GNGOPTX] SMF Ad Hoc and MMF Ad Hoc rescheduled Jonathan In regard to statement given in your presentation, I like to add some more color to this statement • Note: recent work on MPN treatment, by David Cunningham, shown in T11 (Fibre Channel), indicates that FEC is a necessity for 100m links 32GFC operates at 28.05 GBd, current spreadsheet model do show very steep increase in penalty as result of mode partition noise and cross terms. The FC group wants to support 100 m on OM4 fiber, with current noise model even with a simple FFE EQ FEC would be required to close the link budget. Also the same spreadsheet shows that if we added FEC with overhead and operated at 28 GBd instead of 25.78 with 2.5 dBo or 5 dBe penalty we could be worse off than using FEC. So our only option would be to use inband FEC which has higher latency. With 100GNGOPTX investigating 2nd generation set of PMD where there already exist set of solution, as a group we have to deliver a solution which allow seamless migration from 40G-SR4 and is lower cost than 100G-SR10. If it requires fundamental investigation then the group need My concern with current spreadsheet model which I have also shared with David Cunningham is how B (bandwidth) is used for calculation of MPN, for mode partition noise and the cross term for detail analysis please see David presentation B= 1/(T-DCD) where T is the 1/Baudrate σmpn = kOMA/√2 . [1 - e^(-β^2)] I do agree in the ISI calculation we should use DCD to increase the effective baudrate but if you have slow laser which is the case for 25.78 operation both ISI and MPN do not increase the laser is toggling faster but never reaches steady state! The spreadsheet already captures the ISI penalty and double counting might have been negligible at lower speed when the laser were fast but double counting at these speed breaks the link or we end up with a link What seems reasonable here is to use the current B for ISI penalty calculation but for MPN and Cross where Teff is the RMS mean of sqrt(Trise^2+Tfall^2/2) as I expect current Ts is in the spreadsheet On Feb 13, 2012, at 5:52 PM, Jonathan King wrote:
Here is my presentation for the MMF ad hoc call , 14th Feb 2012 This is intended to be an introduction to, and framework for, discussion on what we do as an ad hoc to progress towards an MMF objective. By popular request, we have moved this meeting to Tuesday 14 February at the same time as before. (With apologies to Paul who now can’t attend.) As mentioned by Dan, Jonathan and I are planning to hold an SMF Ad Hoc meeting immediately followed by an MMF Ad Hoc meeting (1 hour each) starting at 8:00 am Pacific on Tuesday 14February. Australia, Brisbane : 0730870163 Australia, Melbourne : 0383380011 Australia, Sydney : 0282386454 Austria, Vienna : 01253021727 Belgium, Brussels : 028948259 Bulgaria, Sofia : 024917751 Canada, All Cities : 2064450056 China, All Cities Domestic : 8008706896 China, All Cities Domestic : 4006920013 Czech Republic, Prague : 228882153 Denmark, Copenhagen : 32727639 Estonia, Tallinn : 6682564 Finland, Helsinki : 0923193023 France, Paris : 0170375518 Germany, Berlin : 03030013082 Germany, Frankfurt : 06924437355 Hong Kong, Hong Kong : 85230730462 Hungary, Budapest : 017789269 India, Bangalore : 08039418300 India, Chennai - Primary : 04430062138 India, Mumbai : 02239455533 India, New Delhi : 01139418310 Ireland, Dublin : 015269460 Israel, Tel Aviv : 37630760 Italy, Milan : 0200661900 Japan, Tokyo : 0345808383 Korea (South), All Cities : 0264903634 Lithuania, Vilnius : 52055461 Luxembourg, Luxembourg : 20881245 Malaysia, Kuala Lumpur : 0348190063 Netherlands, Amsterdam : 0207946527 New Zealand, Auckland : 099291734 Poland, Warsaw : 223070121 Romania, Bucharest : 318144966 Russian Federation, Moscow : 4992701688 Singapore, All Cities : 6568829970 Slovak Republic, Bratislava : 0233418490 Slovenia, Ljubljana : 016003971 Spain, Barcelona : 935452633 Spain, Madrid : 911146624 Sweden, Stockholm : 0850512711 Switzerland, Bellinzona : 0912611463 United Kingdom, All Cities : 08443386571 United Kingdom, All Cities : 02034333547 United States, All Cities : 4438636577 Vietnam, Ho Chi Minh : 84838012419 Pete Anslow | Senior Standards Advisor
43-51 Worship Street | London, EC2A 2DX, UK
Direct +44 2070 125535 | John, Steve;
Thanks for this contribution to the forward progress of the Study Group.
I would like to ask that our participants take the time to open the links below and refresh themselves on these points.
In my experience, the tendency for a Study Group to get distracted is not new, and the need to continually remind ourselves of where we are in the process is essential.
I would add that each project has its own unique characteristics and therefore the process provides boundaries but the path will always be slightly different. Given that we (100G Ethernet) have optical PMDs which already exist and satisfy broad market potential, it changes the relative importance of the 5 criteria responses. We are not just comparing ourselves to prior speeds or other media types, but to 100G PMDs that are currently available. We need to be distinct, economically feasible against those alternatives in order to meet the needs of a broad market, and demonstrate we are technically feasible as well.
Your advice is appreciated and we should all be diligent to remain within the process boundaries and seek a path that brings us to a successful PAR and 5 criteria response. In that regard, focus on the process is essential.
Jonathan and Pete are in the process of setting up a co-joined adhoc meeting that will address objectives and 5C responses for both the MMF and SMF technologies. We hope to provide that focus, and define a path for forward progress.
Best Regards,
Dan <MMF-objective-Next-Steps.pptx>
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