On Thu, Jul 18, 2024 2:55 AM Parsons, Earl <00002109e8f11cc7-dmarc-request@xxxxxxxxxxxxxxxxx> wrote:
Hi John,
I can serve as champion.
Thanks.
- Earl
From: Chris Cole <chris.cole@xxxxxxxxxxxx>
Sent: Wednesday, July 17, 2024 2:39 PM
To: STDS-802-3-B400G-OPTX@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_B400G_OPTX] Dispersion for 400G lanes
The champion should be a fiber expert.
I am always happy to help out.
Chris
Chris – do you wish to be the champion?
If not – then Earl or Frank?
I also agree.
Thanks.
- Earl
I agree with John! Let’s move this discussion (which is good!) to the NEA.
That way it won’t disrupt the good work in .3dj.
Frank E
All,
While I appreciate the benefits of us looking to the future, at this point we have not selected a 400G per lane (assuming based on PAM4)based
solution, let’s be careful with our discussions so that people do not think we are now considering adding objectives.
As IEEE P802.3dj already has enough PMDs to resolve I would suggest we focus future needs discussion elsewhere, such as the NEA.
Regards,
John
All,
Before we start proposing such innovative ideas, can we have a level set on what it is we are trying to achieve?
I mean, 400G per wave means 4 times less dispersion than 200G. 4 is a big number. I think it is very unlikely that fiber specs are going
to achieve that much improvement, no matter what you do. But, what is it that we are trying to do?
Are we talking of an FR4 or an LR4 kind of link, and what wavelength plan?
Thanks,
Frank E.
Hi All,
Here’s a new thread for the dispersion considerations for 400G lanes.
If we want new CD fiber specs for 400G lanes, now is the right time to start those conversations.
For multimode CD specs we limit the range of wavelength and slope together. For example, the OM4 standard has a triangular region of compliant wavelengths and slopes that looks something
like this:
<6238037585377053067>
For SM we might want to consider a trapezoid shape like this:
<6812754313763279652>
I think it would be easier for fiber manufacturers to comply with this shape with their existing product than narrowing the zero-dispersion wavelength range like Chris proposed earlier
on the reflector. Snipping of the top “corners” of the CD spec range could give the same reduction in max/min dispersion.
We could also take a page from IEC connector standards. For different connector grades IEC specifies random mate connector attenuation such that “probability of a random mated connector
set of meeting or exceeding the specified level of attenuation will be ≥ 97 %.” A new fiber standard could specify that >99% of a manufacturer’s fibers fall within the trapezoid.
Thanks.
- Earl
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