Re: [802.3_DWDM] IEEE P802.3cw Optical Crosstalk Ad hoc

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Again while reading G.698.2 I came across the following two sections that appear to constrain the maximum inter-channel and interferometric crosstalk.

They are both very clearly written and define crosstalk as the maximum impact from all of the “disturbing channels” to the “wanted channel” (which I think we have been calling the “channel under consideration” in recent discussions). One could also argue that we might be able to replace the term “disturbing channels” with “alien channels” , to better align with the BaseT analogy that David law brought up on the recent call.

Is there a reason why we need to do something different in the IEEE (i.e. is this G.698.2 approach insufficient for some reason ?).

Gary

From: Gary Nicholl (gnicholl)
Sent: Friday, December 11, 2020 8:59 PM
To: Eric Maniloff <eric.maniloff.ieee@xxxxxxxxx>; STDS-802-3-DWDM@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3_DWDM] IEEE P802.3cw Optical Crosstalk Ad hoc 02 Dec 2020 Material uploaded

I have a question for the group.

I went back to look at G.698.2 to try and better understand the definition of “black link” following the confusion on the call the other day, and specifically to try an understand if the black link only applies to a single-channel connection (S_S and R_S) between a single transmitter (Tx) and receiver (Rx) or whether the term black link applies to the multitude of single-channel connectors (Ss and Rs) that run over a single “DWDM link” (using G.698.2 terminology) or what we would call “DWDM System” (using IEEE terminology).

To be honest after reading G.698.2 I am none the wiser. However what I did discover is that the ITU and the IEEE are using the term “DWDM Link” to mean two very different things.

Based on Figure 5-1 (above), G.698.2 is using the term “DWDM link” to refer to a multitude of single-channel connections (Ss to Rs) excluding the associated transmitters and receivers, whereas the IEEE defines the term “DWDM link” to refer to a single-channel connection (between a single Ss and corresponding single Rs) and including the associated single transmitter (Tx) and receiver (Rx). See what is highlighted in green below.

https://www.ieee802.org/3/ct/public/19_11/dambrosia_3ct_01_1119.pdf

Any thoughts or comments to help address my confusion ? I think until we are sure we are all using the same terminology it is going to be hard to make progress (especially when we get into more of the subtle details).

Gary

Ps. Perhaps one thing that is missing from the IEEE is a name for the single entity that comprises the multitude of single-channel (Ss to Rs) connections that run over the same “DWDM System” ( which appears to be what is referred to as a “DWDM link” in G.698.2 ?). This would be the blue box below. Maybe it is not necessary for this to be defined (or given a name) in the IEEE ? One could argue that since the IEEE PHY is defined as a single-channel , from a specific Ss/TP2 to the corresponding Rs/TP3 (essentially a slice through the blue box shown below) that it is out of scope to refer to or discuss the multitude of other single-channel (Ss to Rs) connections that run over the same DWDM System/Link ?

From: Eric Maniloff <eric.maniloff.ieee@xxxxxxxxx>
Sent: Monday, December 7, 2020 6:10 PM
To: STDS-802-3-DWDM@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_DWDM] IEEE P802.3cw Optical Crosstalk Ad hoc 02 Dec 2020 Material uploaded

Hi Bo,

The presentation that you showed had different filter sets providing the same passband for the signal channel. My presentation last week was based on the isolation between the signal channel and crosstalk on adjacent ports. The key here is that defining only the signal channels' bandwidth isn't sufficient but the impact on other ports needs to be considered.

Including this additional definition removes the need to specify individual components inside the black link. So the test points won't be changed, TP2 and TP3 will still be the relevant points for Black Link measurement. What will be included is additional information on the black link's transfer function.

I had some other questions related to the measurement slide, I think when I expand on this on this week's ad-hoc call it should be more clear.

Regards, Eric

On Thu, Dec 3, 2020 at 3:09 PM Bo Zhang <bozbozboz@xxxxxxxxx> wrote:

Hi Eric,

To John’s encouragement of leveraging the reflector, I would like to pick up from where we left off from the ad-hoc. Specifically to your last slide in your contribution, what do you envision as the needed work items in the P802.3cw draft if we were to further your approach for black link test methodology for crosstalk parameter.

From my perspective, I see one needs to understand below items at a minimum

The exact stimulus (whether it’s broadband or tunable light or an actual 400G ZR Tx or something else)
The exact response (whether it’s integrated power or spectral contents or something else)
The exact stimulus test points (whether it’s TP2, TP2’ from adjacent channels)
The exact response test points (whether it’s TP3, TP3’ from adjacent channels)
The test conditions of the black link (in terms of BA and PA settings as compared to in-service mode)

Also, for your initial isolation value recommendation, what’s your view when it applies to the counterexample I gave in slide 13 of my Nov. 16^th P802.3cw presentation

Thanks,

-Bo

On Wed, Dec 2, 2020 at 3:36 PM John D'Ambrosia <jdambrosia@xxxxxxxxx> wrote:

All,

The material for today’s IEEE P802.3cw Optical Crosstalk Ad hoc meeting has been uploaded and may be found at https://www.ieee802.org/3/cw/public/adhoc/20_1202/index.html

Please note I have not completed meeting notes yet, but wanted to get the technical material uploaded for all to begin reviewing.

Regards,

John D’Ambrosia

Chair, IEEE P802.3cw Task Force

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-Bo

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Re: [802.3_DWDM] IEEE P802.3cw Optical Crosstalk Ad hoc - a question on how G.698.2 defines "Maximum inter-channel crosstalk" and "Maximum interferometric crosstalk"