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Re: [802.3_NGECDC] 04 June Webpage Update

Hi John,

 

Looks like I missed an exciting meeting and the start of another Ethernet optics journey.

 

In reviewing the presented material, I noticed that my friend Jim fell into the classic trap of assuming that a straight line trend will always stay linear.   

 

http://ieee802.org/3/ad_hoc/ngrates/public/calls/20_0604/theodoras_nea_01_200604.pdf#page=2

 

Fortunately for engineers, our world is more interesting, otherwise we could be replaced by accountants.

 

For loss dominated links (LossLINK), like inside the datacenter, with equal laser power, the SNR advantage of Coherent (CH) over Direct Detection (DD) is

 

SNRCH-DD = LossLINK + 2*LossDD_TX - LossCH_TX (dB)

 

For typical datacenter link loss, like 4dB, and typical Transmitter (TX) implementations, the first two terms are less than the third term. This means that Direction Detection SNR is higher and to match it Coherent requires more laser power. Further, the Coherent laser requires more power for cooling, and Coherent MZMs require more power to drive than Direct Detection DMLs or EAMs.

 

In the Stuff Table, apples are added to oranges, cherries, grapes and others to arrive at a fruit salad total. Coherent MZMs are larger than intensity modulators.  One Coherent laser is larger than the lasers in 4 or 8 EMLs or DMLs. Coherent requires a 4:1 transmitter combiner, not a 2:1.

 

When we get into Study Group, let’s do the math before choosing a technology.

 

Chris

 

P.S. Sadly, I couldn’t find anything in Matt’s presentation to pick on.

 

From: John D'Ambrosia <jdambrosia@xxxxxxxxx>
Sent: Monday, June 08, 2020 4:42 AM
To: STDS-802-3-NGECDC@xxxxxxxxxxxxxxxxx
Subject: [802.3_NGECDC] 04 June Webpage Update

 

All

The unapproved minutes for the 04 June Teleconference have been uploaded - http://www.ieee802.org/3/ad_hoc/ngrates/public/calls/20_0604/minutes_nea_200604_unapproved.pdf

 

Please review and contact myself or Jon Lewis with any potential modifications.

 

Regards

 

John D’Ambrosia

Chair, IEEE 802.3 NEA Ad hoc

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