Re: [802.3_NGEPON] 802.3ca (100G-EPON) bi-weekly consensus - call for agenda items

[Francois Menard <fmenard@xxxxxxxxxxx>]

Folks,

Please allow me to add some comments to this discussion. I will limit the scope of my apropos to the channel(s) in the direction of the ONU from the OLT.

I would not say the situation is as grim as an insertion loss of 4 dB’s for the 4-channel Mux/Demux function requiring AWG, as the insertion loss can be better with more sophisticated integrated optics filters than AWG’s such as contra-directional couplers.  

It strikes me that in the 100Gps ONU, what remains a constant source of costs is the requirement for 4 of everything (APD’s, TIA’s, Limiting Amplifiers, Dispersion Compensation) in order to achieve 100Gbps.  It is unclear to me whether APD vendors would be able to cost reduce an array of four APDs, but I suppose anything in volumes of millions is worth its weight melted at the metal yard.

My point is that in contrast to NG-PON2,  should the ONU receiver in NG-EPON not be tunable, then NG-EPON ONU’s which will implement fewer than 4 channels, will be hardcoded to certain channels, removing the flexibility of dynamic bandwidth assignment across all NG-EPON channels.  The same of course apply to an NG-EPON ONU cost reduced to a single 25G channel.

Another point, is that should the number of channels be greater than four, say 12 or 16 (16x25 = 400 Gbps on the PON), then even if there is 4 of everything in the ONU (APD’s, TIA’s, Limiting Amplifiers, Dispersion Compensation), then ideally, all of the four receivers in the ONU would need to be tunable across the range of 12 or 16 channels.  

I would recommend that NG-EPON keeps implementation flexibility to support tunable receivers.

-=Francois=-

From: Liudekun <liudekun@xxxxxxxxxx>
Reply-To: Liudekun <liudekun@xxxxxxxxxx>
Date: Wednesday, February 17, 2016 at 05:01
To: "STDS-802-3-NGEPON@xxxxxxxxxxxxxxxxx" <STDS-802-3-NGEPON@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_NGEPON] 802.3ca (100G-EPON) bi-weekly consensus - call for agenda items

Hi Marek

  I agree with you “the module cost increase is not really linear in the function of integrated channels”

 

Actually , optics integration hasn’t save  cost compared with discrete components by far,  due to the limited yield for optic chips .(This is contrary on electronic chips, VLSI).

A 4 Tx array are more than 4 times expensive than a single channel Tx, due to the yield is the multiplication of single chips’ yield.

For the  package process of optics, especially the coupling, active coupling (need a light source during the coupling) combined with manual adjustment is still the major technology in nowadays ,  so align a 4 channels array to a fiber array are much more complicated  than a single channel alignment .   All of these make the optics integration still very expensive, more expensive than 4 times of single channel. The more channels, the cost becomes even higher.

 

Another aspect we need to consider is that,  if we consider the interface of  a 100G ONU is same with 1G or 10G EPON ONU,  retain 1 fiber , bidirectional,   then we need a 4 wavelength mux and demux inside the module .  the mux and demux will bring extra cost and extra insertion loss.

 

For a 4 channel AWG, the insertion loss is at least 4dB,  if we consider the cascaded  thin film filter,  the IL is still 2~3dB.   If we want to keep a same output power with current 10G EPON ONUs,  then the transmitter will  need to increase the output power by 3dB, the APD receiver will need to improve its’ sensitivity by 3dB,  this will further increase the cost.  (That’s the miracle ,   when the speed comes high ,the sensitivity becomes low,  but we need  the sensitivity becomes even higher )

(The power budget in PON system is always expensive,  if you want to more power budget, then you need to pay more,  because the margin has been consumed by the splitter. So any components with insertion loss means extra cost on the transceiver.)

 

Best regards

Dekun Liu

____________________________________________________

Advanced Access Technologies Dept. 网络研究接入技术部

Huawei Technologies Co., Ltd. 华为技术有限公司
  Phone: +86 027-59267217  Email: liudekun@xxxxxxxxxx

 

From: Marek Hajduczenia [mailto:marek.hajduczenia@xxxxxxxxx]
Sent: Wednesday, February 17, 2016 5:42 AM
To: STDS-802-3-NGEPON@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_NGEPON] 802.3ca (100G-EPON) bi-weekly consensus - call for agenda items

 

I would like to add a few more thoughts on individual slides:

 

-          Slide 10: I am not really sure how much power saving there can be in disabling wavelengths versus resulting implementation complexity. Consider that disabling wavelengths in downstream would be rather rare, given that there is always some data to be sent downstream to end customers. Trying to load balance and move all traffic across wavelengths to Lambda0 to be able to disable higher order Lambdas would require much more complexity and control of destination per frame than we have today within an 802.3 PHY.
In the upstream direction, given that ONU powers up lasers only for the duration of the burst, any power savings from powering up one versus 2 or 4 lasers would be also marginal. I think an approach with disabling wavelengths would only work if we had a solid study that demonstrated substantial saving of uW/bit/sec versus implementation complexity.

-          On slide 12, “The cost of 50G and 100G optics will be roughly 2x and 4x of 25G optics” – I have been looking for actual data to demonstrate the relationship between number of channels and relative device cost and failed to find anything solid so far. I recall discussion in one of multi-lane 100G Task Forces indicating that the module cost increase is not really linear in the function of integrated channels, but I do not see actual materials on this topic. It might be worth to seek contributions from companies with optical integration experience to discuss maturity and also relative cost curves.

-          Slide 4: a lot of good points here.
I am not sure, though, what value would be for “3rd gen ONU can pretend to be either 1st gen or 2nd gen ONU” – this means that 100G device would operate only as 25G device, which is counterintuitive – why would someone deploy more expensive device up front and not take advantage of its capabilities? Usually, ONUs are deployed in the function of OLT capabilities, i.e., when the OLT becomes 100G capable, ONUs would follow, not the other way around.
On “3rd gen OLT can serve 1st, 2nd, and 3rd gen ONUs” – one point to consider is how far this backwards compatibility really needs to go. I am not sure what the right answer is here, because this mostly depends on relative cost of 50G and 100G devices when compared side by side. If the delta is not that big, deploying 100G up front would save on truck rolls and upgrade complexity and perhaps eliminate some extra complexity in the system design ?
“No Rx/Tx tunability” – we could very much be silent in the spec about tuneability requirements and support is via extensions to MPCP, where the ONU could announce its tuning capability during MPCP discovery and then have channels allocated with REGISTER message. This might open doorway to reuse of some of existing transport grade components, if that makes any economic sense.

 

Marek

 

From: frank effenberger [mailto:frank.effenberger@xxxxxxxxxx]
Sent: Tuesday, February 16, 2016 3:37 PM
To: STDS-802-3-NGEPON@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_NGEPON] 802.3ca (100G-EPON) bi-weekly consensus - call for agenda items

 

Glen and all,

I would caution against thinking that “wavelengths” are like a commodity.  Unlike people, not all wavelengths are created equal, I’m afraid to say. 

Moreover, we don’t allocate individual wavelengths, but actually wavelength bands, with width of which has a huge effect on cost of components.  

This is what the presentations at the last meeting from Ed and I were getting at. 

 

The worst thing is that we are not starting from a clean slate – there is a lot of legacy there, and also other optics defined in the market that could be reused.

All in all, it is a very complex decision to make, and you can’t simplify it to “Keep the number of wavelengths to a minimum”. 

 

Other than that, your basic ideas of the fully flexible kind of system I generally agree with.  Indeed, my preso in Dallas suggested many of these same features. 

They are a nice ‘wish list’ at this point.  The killer question is: can we achieve all of them?  It’s not so clear to me now.

 

Sincerely,

Frank E.

 

 

From: Glen Kramer [mailto:glen.kramer@xxxxxxxxxxxx]
Sent: Tuesday, February 16, 2016 2:05 PM
To: STDS-802-3-NGEPON@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_NGEPON] 802.3ca (100G-EPON) bi-weekly consensus - call for agenda items

 

Curtis,

 

I'd like to discuss the general architecture approach. We had a number of presentations in Dallas leading towards this approach, but since the Dallas meeting was per-TF, we didn't make any formal decisions. In Atlanta, we started looking into various low-level details, but the big picture is left undefined. My slides are attached. All feedback is welcome.

 

Thanks,

Glen

 

On Mon, Feb 15, 2016 at 10:49 AM, Curtis Knittle <C.Knittle@xxxxxxxxxxxxx> wrote:

 

Dear Colleagues,

 

This coming Thursday, February 18, 11:30-1:00 Mountain Time, we will hold an IEEE 802.3ca 100G-EPON consensus building meeting. Please let me know by Wednesday noon (Mountain Time) whether you have requests for agenda time.

 

If I do not receive agenda requests by noon Wednesday, I will cancel the meeting.

 

Thank you!

 

Curtis

 

 

 

 

Curtis Knittle

VP Wired Technologies – R&D

CableLabs

desk: +1-303-661-3851

mobile: +1-303-589-6869

c.knittle@xxxxxxxxxxxxx

 

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Broadband Technology Group

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