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

Thanks for the comments.  

A number of SG presentations have addressed factors that affect link performance:  vibration for automotive applications, bending (installation), temperature (home, automotive and industrial have different environmental requirements).  Mostly these factors show up in the power budget, though other effects (e.g., on bandwidth) have been studied.  As with most PHY projects, the TF will evaluate proposals on how well the proposals deliver performance and what the performance costs.  Making those tradeoffs is a TF responsibility not that of a SG.

Someone in the SG joked at a previous meeting that a really worst case link is a broken fiber.  We all know that some installations of UTP stripped out the twists for many inches at a punch down block (that isn’t a Cat 5 installation), yet we have never considered “stupid” installation like this as part of a worst case channel.   Similarly, wrapping any optic cable around a nail or small post when installing it is beyond a reasonable expectation of a worst-case link that is accommodated in the link budget for any of our PHYs.

We believe we have good test data for those factors that contribute to what the TF will define as the worst case link.  For example that the temperature affects on optical components is known and incorporates into a viable link budget, and that we don’t need to use the same temperature range for home as for automotive.  We have looked at the number of connections with their attenuation and believe they are viable for target markets.  Some criticism has conflated things and inappropriately criticized presentations for not testing over certain temperature or distances, when for example, vibration impact on coupled power is not a major concern for home networks, but can be accommodated in a link budget for automotive applications with automotive's shorter link length requirement.  Basically, I’d postulate that I can come up with a link that is “worse" than what has been accommodated on any of our defined PHYs. Instead of accommodating any “worst case” link, what TFs do is accept that there are reasonable expectations on what has to be accommodated in a worst case link, and I believe our test data covers that.

On your last sentence question, the VDE specification that we cite as proof of technical feasibility (because it has been built and independently tested) included rate adaptation.  Our PAR and other project documents only specify 1 Gb/s.  So, a change in scope to include other speeds would require going through this approval process again with a modified PAR.  Possible to do, yes; but we have been trying to keep things simple.  So there has been no advocacy for other speeds.


On Oct 8, 2014, at 4:41 PM, Ran, Adee <adee.ran@xxxxxxxxx> wrote:

One more point here: most home networks I know and can imagine are limited by the external connection (usually xDSL or cable modem) to less than 100 Mb/s. 1G inside the home would seem sufficient at least until the external connection has higher bandwidth; this is some years away in most of the world. So in a sense, 1G is future proof.
Addressing another one of Peter's concerns: is a worse-than-average POF connection can't really work at 1G, sometimes it would be preferable to have it run at a lower speed than to fail (or just misbehave). WiFi and Powerline networking have similar capabilities. Is there an intent to have a lower speed and auto-negotiation in this project?



From: ROBERT GROW [mailto:bobgrow@xxxxxxx] 
Sent: Thursday, October 09, 2014 2:08 AM
To: STDS-802-3-DIALOG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_DIALOG] Considerations on technical feasibility of 1GE POF and being future proof
Experience, at least from my perspective, indicates you overstate even for the 10 year horizon.  New construction in California at least has included home networking cabling as a feature for decades (I remember it was a feature when I was last house shopping in 1992).  Over subsequent years, the cabling used in new construction has followed the best UTP medium available at construction time.  What POF provides is a great solution for retro-fit.  In some geos though, POF is even growing as the medium of choice for new construction.
An observation I hoped people would draw from my recounting of UTP history is that we have never increased Ethernet speed on UTP without a cabling specification change.  Admittedly, much of the Cat 5 produced met Cat 5e requirements (the closest we have come to a speed increase using the same copper media), but not all Cat 5 or Cat 5 installation met Cat 5e specifications.  There is room for higher speed operation on SI-POF and I view it as being more like Cat 5 in its future potential.
I appreciate your point on not knowing what devices we will be using in the future, and I would add usage models for familiar devices (e.g., how much of what we watch on TV will be on demand, without any broadcast timing constraint, rather than traditional channel broadcast of content).  The confidence in these predictions has to be lower that was the confidence of the cabling industry that Cat 6 was future proof.
POF is being installed for both new and retrofit in home networks today.  While Europe and Asia are further along in this adoption than is North America (much because they are hitting problems with Wi-Fi that requires a cabled home backbone to overcome), there is some positive experience in North America.  Other geos (e.g., South America) show indications of coming up against the same challenges that Europe has seen as their adoption and usage of networked services accelerates.
While we all want home networking cabling to have a long lifetime and future for increased usage, realistically it is very difficult to predict when and to what speed bandwidth demand within a home will increase.  And, there is always going to be the tradeoff between cost and simplicity of a medium against higher confidence in future capability.  
On Oct 8, 2014, at 1:41 PM, Trowbridge, Stephen J (Steve) <steve.trowbridge@xxxxxxxxxxxxxxxxxx> wrote:

Hi Bob & Peter,
I agree that 30 years is a little extreme: nobody can predict where technology will be in that kind of horizon.
But I do share the concern that you wouldn’t be likely to deploy a home networking solution that requires installation of new cabling throughout your house unless you were confident the cabling would be good for 10 years. You surely don’t want to be doing fresh cable installations for something that looks unlikely to carry you for one speed step beyond what you can get in the first generation product.
Seeing the CFI for November for taking what you can do over 100m Cat5/6/6A cabling up to 2-5G, I would think the degree of being “future proof” for new cabling would be that you have confidence it would work at those speeds. If upgrading in your house from 802.11N to 802.11AC would drive you beyond the capacity of cable you installed in the next year or two, I think it could be argued this wasn’t future proof.
From: ROBERT GROW [mailto:bobgrow@xxxxxxx] 
Sent: Wednesday, October 08, 2014 2:01 PM
To: STDS-802-3-DIALOG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_DIALOG] Considerations on technical feasibility of 1GE POF and being future proof
I will take issue with your 30 year criteria for home networking.  You certainly are entitled to that opinion, but I believe it unrealistic, and accepting the 30 year criteria forces one to conclude Ethernet is not viable as a home network technology, something both history and market input to our study group argue against. Why do I come to that conclusion?  Let’s just look back 20 years.  
What was the state of Ethernet?  The approved standard included 10BASE-T and p802.3u was working to specify 100BASE-TX and 100BASE-FX.  The media for those:  Cat 5 and primarily 100/140 multimode fiber.  In the last 20 years, 802.3 has moved from Cat 3 for 10BASE-T to Cat 5 for 100BASE-TX, then we needed Cat 5e for 1000BASE-T, Cat 6A for 10GBASE-T (the cable industry’s best guess for a future proof cable before 10GBASE-T was Cat 6), etc.  Similarly, MMF has moved to 62.5/125, then we got higher bandwidth MMF.  
Optics experts might correct me, but the only media in use 20 years ago that we use today for 1 and 10 Gb/s was single mode fiber (I haven’t researched what changed on types of SMF).  But SMF is not friendly for home network use for both technical and ease of installation reasons.
I was a participant on a cabling discussion group decades ago.  I still remember a question that was similar to your requirement.  “I'm building a 22,000 sq. ft. house (2044 sq. m.) and I don’t ever want to have to replace the data cabling.  What should I install?”  My answer was conduit with a pull string.  Then I also provided my opinion for the best copper and fiber options at the time, none of which is a preferred medium today.  
Looking at our history with reuse of media as speed increases, my answer from decades ago still has validity.  And guess what.  For markets where POF is being demanded, that is exactly what exist.  Conduit available for POF installation, and if you install SI-POF as has been proposed to the GEPOF SG, you can use it as a pull string if cabling needs to be upgraded to GI-POF or some other non-conductive medium.
On Oct 8, 2014, at 6:08 AM, Peter Stassar <Peter.Stassar@xxxxxxxxxx> wrote:

Hi Bob,
Thanks for your email response sent about 3 weeks ago.
I would like to start to re-emphasize that my main concern was in the end of the email which I sent on 22 July:
In conclusion I have not been convinced that 1Gb/s Ethernet over 50m of worst case POF  is technically feasible and even more that an installed POF link can be upgraded to higher speeds, which I believe is necessary to justify long lifetimes of home-installed POF networks.”
As you suggested I took a close look to the presentations to the meeting in Ottawa, 4 weeks ago.
Before commenting to those I will first address the 5 points from your email. I inserted comments in “red in the thread below.
So back to the September presentations.
In Eugene_GEPOF_01_0914 I see a strong claim that POF is future proof and that it is superior to existing technologies like twisted pair, coax and power line. This presentation also says “Tomorrow SMART HOME needs future proof networking medium”, which is a statement which I fully support and, I believe, have always clearly stated. This is however also the weak point of all presentations which I have seen so far. I continuously fail to find any evidence that POF and the 1GbE technology to work with it, is sufficiently future proof. In Tsukamoto_GEPOF_02_0914 the following is said  “Customers may use the network over 30 to 50 years. Is GbE enough in such a far future?”. This is exactly the point I tried to make during the CFI consensus building meeting in Beijing and during the San Diego meeting. It’s my strong belief that 1 Gb/s is NOT sufficiently high speed to justify deployment of POF in the home. Some references have been made to shorter wavelength windows of POF which could provide lower attenuation than at 650nm. Having looked at the Ottawa presentations I see some inconsistencies. While in Eugene_GEPOF_01_0914 I see a claim that in the range 450 to 580 nm the attenuation will be lower than at 650 nm, I conclude from Tsukamoto_GEPOF_01b_0914 that the POF standard is only specified for the 650nm window and that therefore operation is other wavelength windows is not specified and thus not guaranteed. A lower attenuation in the range 450 – 580nm would indeed be great, but what will be the bandwidth of POF in that wavelength range? It is not trivial that it will be the same or better or worse. I am under the impression that POF is a kind of multimode fiber and bandwidth is strongly dependent on the wavelength.
In conclusion, having looked in detail at the presentations to the Ottawa meeting and the clarifications in your email, I am still of the opinion that insufficient evidence has been provided that the proposed solutions are capable of multi-vendor interoperability (capability of developing a multi-vendor interoperable transceiver design from the specification under worst case conditions) and that the POF medium is sufficiently future-proof (or in other words upgradeable to speeds well in excess of 1Gb/s) to justify installations in the home for many decades to come.
Kind regards,
Peter Stassar, 施笪安
Technical Director, 术总监
Huawei Technologies Ltd, 华为技术有限公司
European Research Center, 欧洲研究所
Karspeldreef 4, 1101CJ Amsterdam
The Netherlands
Tel: +31 20 4300 832
Mob: +31 6 21146286
From: ROBERT GROW [mailto:bobgrow@xxxxxxx] 
Sent: Monday, September 15, 2014 6:57 PM
To: STDS-802-3-DIALOG@xxxxxxxxxxxxxxxxx
Subject: 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.

Peter: I just looked at the available documentation. I understood that many were addressing the 15m automotive market.

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. 

Peter: I do understand the 15m objective. I only put some questions marks on the testing done on 15m links. In the optics world a laboratory test on a TYPICAL fiber is completely different from a test on a worst case fiber under worst case operating conditions. Worst case conditions have a big impact on maximum loss and (I assume for POF) also on bandwidth. Therefore optics people are generally not convinced by a laboratory test on just 15 km of typical fiber. What kind of margins are available, etc.

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. 

Peter: I am of the opinion that details on how to actually “do it” needs to be provided by presentations and not via verbal clarifications. I understand that often things are a given for a limited group of people, but I also think you are very much aware that in 802.3 one needs to convince 75% of the plenary and not only the “insiders”.

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.

Peter: Thanks for pointing this out. It would be great to see some evidence of those different implementations and interworking testing. I am under the impression that all test results shown at the September meeting (Lichtenegger_GEPOF_0914 and perezaranda_GEPOF_01_0914)  were from the same PHY vendor and not between PHYs from different vendors. So it would have been very interesting to see results from interoperability testing between devices from different vendors.

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.

Peter: regarding to your statement “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)”, I would like to point out that for optical PHYs many years of (bad) experience have taught most optical engineers that simulations in the optical field in most cases need to be confirmed by experiments in order to judge the accuracy of the simulations. That’s why I (and probably not only myself) keep repeating that to demonstrate technical feasibility of Optical PHYs results from simulations are generally not sufficient.

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.  

Peter: on the topic of worst case channel I am NOT referring the range of environmental characteristics, despite the fact that they do play a significant role. I am referring to an optical link model with worst case characteristics appropriate for a distance of at least 50m. A test with a spool of 50m of typical POF is generally not regarded as testing a link under worst case conditions. I am under the impression that in many in-force optical specification in 802.3 a lot of work has been done on defining a worst case channel. This generally is defined such that it will support manufacturers in designing, manufacturing and testing transceivers. Performing a test on a spool of 50m POF is indeed proof of concept, but by far not enough to claim complete technical feasibility, or in other words sufficient maturity of the technology that it actually can be manufactured in high volume and with a high yield, work on worst case links of 50m POF in the home in a multi-vendor environment. I am afraid that this has not yet been demonstrated. The fiber shown on page 16 of perezaranda_GEPOF_01_0914 had an attenuation of 0.19 dB/m, but according to page 5 of Tsukamoto_GEPOF_01b_0914.pdf, IEC 60793-2-40 category A4a.2 has a maximum loss of 0.4 dB/m.  What was the bandwidth of the test fiber and how does that relate to the worst case specification?

Furthermore it was not my intent to criticize those presentations not covering the home market. If I came across to criticize them then I apologize for that. I was just putting remarks to those presentations what they were aimed at and what they were not aimed at.

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