Hi Chris,
I support this proposal of having two objectives for the 10km reach – LR4 and LR1. It is clear that there are two application areas that have different needs and requirements. Having the two objectives
will allow the solutions to be better optimised for the applications they are serving.
Regards,
Mark Kimber
From: Chris Cole <chris@xxxxxxxxxxxxxxx>
Sent: 14 February 2023 00:41
To: STDS-802-3-B400G@xxxxxxxxxxxxxxxxx
Subject: [802.3_B400G] 10km over duplex SMF objective
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Caution: This email originated outside of Semtech.
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During last week's meeting, there were a number of excellent presentations which gave us a clearer picture of the 10km over duplex SMF objective.
Williams showed that the IMDD LR4 solution can result in the lowest cost if it leverages high
volume DR4 and FR4. (Spoiler alert: DR4 and FR4 PHYs will support LR4.) He further showed that the
Coherent LR1 solution can have an unallocated link budget which can be used to support greater reach.
We know that LR1 can easily have an even greater unallocated link budget which can be used for high-loss short-reach intra-datacenter applications like optical switching. This suggests that in the Task Force there are multiple important constituencies which
will not be well served by one solution.
Other presentations showed that there is important technical work that needs to be done and decisions that need to be made. An IMDD example is the FWM penalty. A Coherent example is O-band vs. C-band. The IMDD and Coherent technical issues and decisions are
distinct, and their investigations are decoupled. After discussing this and process issues with our distinguished Chair, John D’Ambrosia, we would like
to propose to the Task Force that we replace the following objective:
Define a physical layer specification that supports 800 Gb/s operation:
· over a single SMF in each direction with lengths up to at least 10 km,
Define a physical layer specification that supports 800 Gb/s operation:
· over 1 wavelength over a single SMF in each direction with lengths up to at least 10 km,
· over 4 wavelengths over a single SMF in each direction with lengths up to at least 10 km.
These two objectives are distinctly different, and examples can be found in prior projects, as well in 802.3dj itself, which has objectives targeting 800
GbE 2km operation over either 4 parallel fibers or 4 wavelengths.
We would like to get your feedback on this approach, and incorporate received comments into a proposal to be made during the March Plenary meeting.
Thank you
Chris
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