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Re: [802.3_DIALOG] Considerations on technical feasibility of 1GE POF and being future proof


Thank you for documenting your concerns following the July plenary meeting.  We reviewed your concerns during our interim Study Group meeting, and I offer some general response.  I believe these thoughts are consistent with the consensus of the GEPOF SG.  Detailed responses to your specific points will likely follow from me and others.  A few general points:

1.  We have certainly noted your acknowledgement that you are satisfied with POF applicability for two of the three markets our participants want to address (i.e., automotive and industrial).  Study Group members though did express some confusion because many of the presentations you choose to comment about were clearly only addressing requirements for the automotive market.  Please see September presentations for additional support for the application to home networking.

2.  In response to your repeated comment “15m (typical?)”, yes 15  meters is the requirement for automobiles.  That is reflected in one of our link length objectives for 15 meters with four in-line connections.  If you look, you will see similar 15 meter objectives for p802.3bp and p802.3bw. 

3.  You also frequently commented on the lack of detail on modulation techniques.  We apologize for that, your question would have been answered if you had been able to attend SG meetings.  In defense of SG presenters, please understand that most of our participants helped develop a VDE specification for operation at up to and including 1 Gb/s with link lengths consistent with our automotive and home reach objectives.  Consequently, much is assumed to be a given with those folk, and it is perhaps excusable that presenters did not have an outside reader trying to understand everything from only the presentation in mind when preparing the presentation. 

There are implementations of the VDE specification from multiple vendors.  All tests that used a PHY used one of these implementations.  If you look at September presentations, you will see that additional presentations on testing include detailed one slide summaries of the characteristics of the VDE PHY.

4.  You also repeatedly commented that simulation was not sufficient for justification of technical feasibility.  While you are entitled to that opinion, but give no rationale why simulation is not valid for demonstration of technical feasibility, I would point out that we have approved projects in the past based on simulation (in my personal experience as far back as 1000BASE-T).  Please also note that simulation is listed in IEEE 802 rules as an acceptable evidence of technical feasibility.

As is true for most engineers, the participants in our SG find it useful to look to both simulation and lab testing and when possible implementation tests expecting consistency.  As noted in my point 3, many of the test presentations you critiqued used an existence proof of technical feasibility – an implementation of the VDE specifications tested at 1000 Mb/s.  We do not only relay on simulation as some previous 802.3 projects have.

5.  You also repeated in your comments a question about worst case channel.  Please note that the environmental requirements for automotive applications have higher temperature, greater EMC, and specific connector requirements.  Industrial applications similarly will also have higher temperature than home, and greater EMC challenges.  While vibration effects on optical power is important for the automotive channel, it is not considered relevant to the channel for nome networking, so our participants have looked at the effects of vibration on optical power, and consequently the automotive channel will include losses for vibration.  With our three major markets asking for a standard POF solution, and different objectives that address those markets, it is appropriate for a presentation to focus only on one particular market application, and unfailr for you to criticize those presentations for not also covering the home network application.  

Please see September and upcoming November presentations for additional support of feasibility for home networking.