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Hi John
Correct again, although looks like the language in my emails may be unclear.
Here is another cut at it.
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PSM4 was first introduced (proposed) in 802.3 in the 802.3bm project
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PSM4 was not adopted in 802.3bm
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100G PSM4 was standardized in an MSA after 802.3bm failed to adopt it
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PSM4 was adopted in 802.3 in the 802.3bs project as 400G DR4
I hope this clarifies it.
Chris
From: jdambrosia@xxxxxxxxx <jdambrosia@xxxxxxxxx>
Sent: Wednesday, July 1, 2026 12:52 PM
To: Chris Cole <chris.cole@xxxxxxxxxxxx>
Cc: STDS-802-3-400GPL@xxxxxxxxxxxxxxxxx <STDS-802-3-400GPL@xxxxxxxxxxxxxxxxx>
Subject: RE: [802.3_400GPL] [400GPL] Website updates
Chris
I just reviewed the 802.3bm specification.
Here are the PMDs defined –
- 85. Physical Medium Dependent sublayer and baseband medium, type 40GBASE-CR4 and 100GBASE-CR10
- 86. Physical Medium Dependent (PMD) sublayer and medium, type 40GBASE–SR4 and 100GBASE–SR10
- 87. Physical Medium Dependent (PMD) sublayer and medium, type 40GBASE–LR4 and 40GBASE–ER4
- 88. Physical Medium Dependent (PMD) sublayer and medium, type 100GBASE–LR4 and 100GBASE–ER4
- 89. Physical Medium Dependent (PMD) sublayer and medium, type 40GBASE-FR
- 92. Physical Medium Dependent (PMD) sublayer and baseband medium, type 100GBASE-CR4
- 93. Physical Medium Dependent (PMD) sublayer and baseband medium, type 100GBASE-KR4
- 95. Physical Medium Dependent (PMD) sublayer and medium, type 100GBASE-SR4
None of these appear to be a PSM solution.
So maybe somewhere else between bm and bs. But that is for another day.
Have a happy holiday.
John
From: Chris Cole <chris.cole@xxxxxxxxxxxx>
Sent: Wednesday, July 1, 2026 3:27 PM
To: John D'Ambrosia <jdambrosia@xxxxxxxxx>
Cc: STDS-802-3-400GPL@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_400GPL] [400GPL] Website updates
John
That is correct.
PSM4 was first introduced in bm, as were other solutions for SMF 100G point-to-point. At the time, our interpretation of Broad Market Potential was that there can only be one solution for SMF. Because there was genuine justification
for multiple ones, bm did not adopt any new one.
This resulted in 100G PSM4 and 100G CWDM4 standardization in MSAs right after the project.
The bs project recognized need for multiple solutions, which established the paradigm we have today of DRn, FRn, and LRn. Break-out application was recognized as a possible use of DRn, although not explicitly specified.
Chris
Chris
400GBASE-DR4 for PSM4 was defined in 802.3bs- not the 100G project as noted below.
500m was selected at the time due to concerns on closing the budget for 2km.
i’m glad to see the notion of breakout included in the 802.3dj standard.
john
Sent from my iPhone
On Jul 1, 2026, at 1:22 AM, Chris Cole <chris.cole@xxxxxxxxxxxx>
wrote:
It's interesting to reflect how on how far DRn has come, from it's introduction as PSM4 in the 100G SMF project, where it was one of many competing point-to-point proposals to today where it's the defacto datacenter optic, although
primarily as break-out.
https://ieee802.org/3/100GNGOPTX/public/nov11/petrilla_01_1111_NG100GOPTX.pdf
[ieee802.org]
Chris
Dear Colleagues,
A majority of the contributions for the upcoming 30 June 2026 electronic teleconference interim meeting were posted. See:
https://www.ieee802.org/3/400GPL/public/260630/index.html [ieee802.org]
With regards,
-Kent
Kent Lusted
Chair, IEEE 802.3 400Gbps/lane Signaling Study Group
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