Re: [802.3_DWDM] IEEE P802.3cw Optical Crosstalk Ad hoc 02 Dec 2020 Mate

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Peter,

All I am trying to do is understand 😊

I understand and agree that G.698.2 is basically talking about single-channel optical interfaces and often refers to “….. for single-channel connection (SS and RS) between transmitters (Tx) and receivers (Rx).”

This is aligned with the term “DWDM Channel” that we defined in 3ct/3cw.

The only other point I was trying to make is that in Figure 5-1, the light grey box is labelled “DWDM link”, which would appear to be the aggregate of ALL of the “single-channel connection (SS and RS) between transmitters (Tx) and receivers (Rx)”. This is clearly different to the definition of “DWDM link” we came up with in 3ct/3cw.

I think what you are telling me is that I am reading too much into the wording “DWDM link” inside the light grey box in Figure 5-1 ?

Gary

From: Peter Stassar <Peter.Stassar@xxxxxxxxxx>
Sent: Monday, December 14, 2020 9:59 AM
To: Gary Nicholl (gnicholl) <gnicholl@xxxxxxxxx>
Cc: STDS-802-3-DWDM@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3_DWDM] IEEE P802.3cw Optical Crosstalk Ad hoc 02 Dec 2020 Material uploaded

Hi Gary,

So, I may have said before, I regret that I wasn’t able to continue my participation at the call of last Wednesday.

I am not sure what you are trying to do, but trying to conclude a definition from a Figure in G.698.2, for which the text states “Figure 5-1 shows a set of reference points, for the linear "black link" approach, for single-channel connection (SS and RS) between transmitters (Tx) and receivers (Rx).” The purpose of Figure 5-1 is only to show the reference points, read TP2 and TP3. Trying to conclude definitions from it is not the right approach.

If you can’t find the term “DWDM link” in G.698.2, it because it’s not there.

So thus by default you can’t state that those definitions in ITU and IEEE 802.3 are not compatible.

G.698.2 is specifically “This Recommendation defines and provides values for single-channel optical interface parameters of physical point-to-point and ring DWDM applications on single-mode optical fibres through the use of the "black link" approach. The black links covered by this Recommendation may contain optical amplifiers.”, which is in the Scope of G.698.2.

I believe that this is exactly the same thing as we want to do in IEEE 802.3.

So it’s a single channel thing, where there is interference inside from other channels present, which is the same problem as we are discussing in cw.

Kind regards,

Peter

From: Gary Nicholl (gnicholl) [mailto:00000bb92642e11e-dmarc-request@xxxxxxxxxxxxxxxxx]
Sent: Friday, December 11, 2020 9:59 PM
To: 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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