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Dan, While leaving aside the issue of whether we should have a
single-mode objective or not at this point, I think that if we choose to
not have one then it is my opinion that we should have an objective to define a
chip to module interface as discussed on slide 7 of anslow_01_1111_NG100GOPTX.pdf.
This is proposed to be of the form: Define a 4-lane 100G
chip-to-module interface I think that this should then also be reflected in the 5
criteria responses as removing the gearbox from 100GBASE-LR4 and ER4. My
reasoning for this is that if the Multimode objective were to be fulfilled
using an un-retimed interface, then there would be nothing in the Task Force’s
documentation to justify the creation of a retimed 4 lane interface as well. Regards, Pete Anslow |
Senior Standards Advisor From: Daniel Dove [mailto:ddove@xxxxxxx] SG Participants, To be very frank, I am concerned about whether we are going to be
able to demonstrate the appropriate justification for a single-mode PMD. We have received presentations on various alternative methods of
achieving SMF distances using anything from MTP-SMF to SiPhotonics to
Multi-Level modulation to mid-wave VCSELs. Those, by themselves have not
demonstrated a significant cost improvement over LR4, nor do they demonstrate
broad market potential (cost relates to volume and vice-versa). Please think about whether this project should include an SMF
objective. If you believe it should, prepare to convince >75% of the SG that
it is technically feasible, cost effective (compare against an LR4 optical
module of equivalent size and electronics), and thus will garner a sufficient
market potential to create a SMF objective. Otherwise, we are faced with a decision in January. Do we go to
March Plenary with an MMF objective only (and a basis for developing the 4x25
electrical spec), or do we delay this SG another cycle? I plan to bring in a "5 Criteria" slide set based on
what I believe will be a MMF objective. That slide set will be subject to
revision. If we find need for changes on the MMF element, or addition of the
SMF criteria, this would have to happen in January to make our necessary
March lead-times. Regards, Dan Dove From: Daniel Dove <ddove@xxxxxxx> Hi Folks, Just a gentle reminder for all. The goal of a Study Group is to develop objectives. As engineers, we often get caught up in the details of how things
work, and how we can do them better, etc. This is OK, but we should keep our eye on the target.
Now, this is NOT an objective, but it could be. We only have to do one thing in this Study Group related to
SMF; Identify the the value of Z that meets
the 5 criteria, starting with Market Potential. We may find that there is no
need for a SMF objective, or we may find that there is a need. To demonstrate need, we must
show market potential for an alternative to 100GBASE-LR4 exists, and this is
most likely demonstrated by showing a cost/power advantage can be obtained by
alternative approaches. We have to assume that a 4x25G interface will reduce
module size and power, and hence cost, so our relative comparison is not a CFP
based LR4, but rather a 4x25G electrically interface based LR4 cost model. Agreed? If so, then demonstrating
that a reasonable volume of nR4 (relative to LR4) can achieve a significant
cost/power advantage over LR4, should be the path to securing an objective
for SMF. We can assume that volumes in a data center that exceed SR4 reach
will exist, and will be significant relative to 10Km applications. Of course we
will want to quantify that assumption, but lets run with it. I think breaking down the
relative cost of the optical subsystems and fiber infrastructure (in the case
of MTP arguments), then demonstrating how an alternative approach lowers these
costs, should be the next step. For example, suppose we break down a 4x25G LR4
module into cost components (PCB, Mech, Tx_Optics, Rx_Optics, Si, Filters) and
call that 100%. Then look alternative approaches and lay them alongside
(assuming common volumes) and see where they land. If a particular approach is
limited to Z Km, then look at the market potential for that reach based on
distribution of links that can use it. Is this not a reasonable
approach to the question? If so, then lets use it as a framework for future
presentation. Dan |