| Thread Links | Date Links | ||||
|---|---|---|---|---|---|
| Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
|
Hi Jim,
I think nobody is trying to argue in favour of scrapping
1550-1560 nm band. From the very beginning of the project we always made the
assumption that this band stays where it is. It was also one of the reasons why
we were looking at bands above 1560 for potential digital channel location for
10G signals.
I was also hoping to see some solid data from people
participating in our group and dealing with filter design / having close contact
with filter design. I am not sure what to do in the light of lack of anticipated
contributions related with filter design cost ...I would definitely not like to
spend more time on this topic than absolutely necessary. We still have other
issues to resolve at this upcoming meeting, not less important than wavelength
allocation plan.
Regards and hope You have good weekend
Marek
From: Jim Farmer [mailto:Jim.Farmer@xxxxxxxxxxxxx] Sent: sexta-feira, 7 de Novembro de 2008 18:19 To: STDS-802-3-10GEPON@xxxxxxxxxxxxxxxxx Subject: Re: [8023-10GEPON] FW: Downstream wavelength-continued Marek said it better than I did. Thank
you.
From: Frank Chang To: STDS-802-3-10GEPON@xxxxxxxxxxxxxxxxx Sent: Fri Nov 07 18:54:29 2008 Subject: Re: [8023-10GEPON] FW: Downstream wavelength-continued This is in line with
what I interpreted Jim?s argument earlier. Actually I think option
(3) is part of option (2), the only difference is option (3) favor one
implementation using cooled TX, which significantly increase OLT TX cost and
power. While option (2) is more generic, you can use either TX implementations
(cooled, semi-cooled, or uncooled). From practical
perspective, PR(x)30 will possibly dominate 95% of the actual deployment. And I
feel PR10/20 for most of us is a ?whatever?. In light of this, I
would rather the specs to be more generic for PR10/20 to at least possibly cover
uncooled TX. So I tends toward we
should switch back to option (2) which is D2.0. The question still-
Can anybody elaborate
how PR10/20 going to be deployed, and how it maters?
Frank From: Marek
Hajduczenia [mailto:marek_haj@xxxxxxx] Jim,
so let me try to wrap
it all up because I must admit I am getting lost in here myself. We have now
three options on the table (1) use wavelength
allocation plan as per D2.1 (all 3 PMDs use 1577 +- 3
nm) (2) use wavelength
allocation plan as per D2.0 (1577 +- 3 nm for PR(X)30 and 1590 +- 10 nm for
PR(X)10/20) (3) use something in
between which You propose i.e. 1577 +- 3 nm for PR(X)30 and 1590 +- 3 nm
for PR(X)10/20 Did I get this right ?
Now, in the course of discussion we acquired one new option, which has never
been on the table. As much as it seems to make sense, I am wondering what is the
added gain of specifying new 6 nm band for PR(X)10/20 instead of using the same
band as for PR(X)30. Distance between video overlay edge and the edge of digital
data channel is the only things that comes to my mind. Did I miss anything
? Note also that we have
a number of contradictory comments in our pool for this meeting - some calling
for option (2), some calling for option (3). Regarding the cost of
the resulting filters and the impact of separation gap between video channel
edge and digital channel edge (using relative cost values) - can we have
reliable estimate of how much it would cost to have various filter options
manufactured using e.g. 20 nm CWDM like type 1580 - 1600 pass band filter for
D2.0 PR(X)10/20 ONU as the base cost ? I have seen a number of presentations on
cost filters and usually channel separations on the order of 15 nm between the
edges of adjacent bands are quoted at 110 - 130% of costs of filter with 20 nm
separation between the edges of adjacent bands. Frank I believe can confirm
that. A question then: are they plain old wrong and the cost hit is much greater
? Do You have a way to provide solid values for relative cost in such cases ?
Thank You for this
interesting discussion. I must say that it has been a while since a topic
generated so much traffic on the reflector. regards Marek From: Jim
Farmer [mailto:Jim.Farmer@xxxxxxxxxxxxx] Thanks for the good
comments on this thread. We would like to add a bit
more clarification or our position before we meet next
week. We believe that PR(x)30
can stay at 1577 nm. We would like to see the ability to operate
PR(X)10/20 on 1590 +/-3 nm. We would like to say 1590 +/-10 nm, but this
is not feasible. It requires a wider filter bandwidth, which is more
difficult, as has been pointed out. This is one of the reasons why we
reduced the proposed occupied bandwidth of the 1590 nm option to +/-3 nm, even
though this requires a cooled laser at the OLT. We have reviewed
the presentations from May 2007. While we agree in principle with the
presentations, it seems that they do not take into consideration initial
wavelength calibration of the filter, nor do they take into account temperature
drift of the filter. And since the filter in question is at the ONU, it
must be very low in cost. A filter designed for either 1577 nm or 1590 nm
must be wider than the occupied wavelength range of the laser, in order to
account for initial calibration accuracy of the filter, and the temperature
drift. When we added these effects, the transition region of a 1577 nm
filter (which must attenuate the 1550 nm broadcast signal), became unacceptably
small. The transition region for a 1590 nm filter went to 14 nm, which is
tight but might be possible at ONU prices. This is what we show on the
slides we sent to the reflector earlier, and which we seek permission to present
in We have been talking to
filter experts about how to make low cost filters that will meet the
requirements. One of the experts we have consulted is our parent company's
Dr. Matt Pearson in "He's correct in his comments - 6 nm is
definitely easier than 20 nm (which is why we recommend it in Jim's
proposal!). "He is also correct that both the filters
and lasers are available to meet these specs. (DWDM relies on that!).
Our concern is more related to the costs, where DWDM costs are outrageous,
even CWDM costs are too high for FTTH. So we need noticeably easier specs
than CWDM. In fact, I would argue that we need noticeably easier specs
than today's FTTH..! -- There are so many more expensive aspects to 10G
than 1.25G (DFB, APD, 10G electronics, extra blocking filters, etc), that if
they want any hope of getting optics at a reasonable cost then they have to
compromise something somewhere... "Thin films and DFB lasers can meet either
spec. We believe (certain) PLC technology can also meet either spec.
But some other PLC approaches ... would quite likely never meet
these 10G specs.. So again, it limits the pool of available suppliers and
available technologies that could otherwise help bring down costs for systems
people. "Either way, we will make it work.
We're just trying to make (the cost of the ONU
lower)..." Thanks, jim
farmer Alan
Brown Jim Farmer,
K4BSE
From: Frank
Effenberger [mailto:feffenberger@xxxxxxxxxx]
Victor,
I doubt that.
>90% of EPON is deployed in Back to the Mike?s
suggestion ? while it is a good idea, it will work if the big concern is the
transmitter specifications. However, the latest
comment from Jim Farmer regards the filters at the ONU receiver. And
defining a super-set of the bands doesn?t help there.
Actually, in my
opinion, neither the filters nor the lasers are that big of a deal. I?m
not sure where Jim?s filter data come from, but there are pretty standard
thin-film filter designs that can achieve the sharpness, accuracy, and
temperature stability that we need for 14nm of guard band. Our task force
actually got a model of this back in May of 2007. Actually, one of the
considerations in the difficulty of making these filters is the width of the
pass band, and it is actually easier to make a 6nm width pass band than a 20nm
pass band. Sincerely, Frank
E. From: Marek
Hajduczenia [mailto:marek_haj@xxxxxxx] Hi Victor,
That is how Mike sees
it. That does not need to be necessarily how things work out in the market. It
seems to me that we are trying to guess which direction the market goes and I
think we all agree that is hardly predictable. Additionally, if I recall right,
we are not allowed to discuss market shares so probably it is better to leave it
at this ... Regards Marek From: Victor
Blake [mailto:victorblake@xxxxxxx] To chmine in here
? I?d have to say that to me it sounds like the 1577 is the exception, not the
1590. -Victor From: Marek
Hajduczenia [mailto:marek_haj@xxxxxxx] Hi Mike,
thanks for sharing Your
point of view with us. Please confirm whether
I understand You right. You say that we should go with a wider window and
carriers may require vendors to actually build equipment which complies to a
certain part of this sub-band. In our case, we could hypothetically specify a
downstream band between 1574 and 1600 nm while e.g. a narrow band option between
1574 and 1580 nm could be required by some carriers to remain compliant with
their ODN. Is this what You're trying to relay in Your email ? Please confirm
Thank You
Marek From: Mike
Dudek [mailto:Mike.Dudek@xxxxxxxx] As an outsider to
10GEPON, but member of IEEE 802.3 working group I?d like to suggest that the
IEEE standard should be working to provide the best solution for the new future
installs of the IEEE standard while paying attention to the existing
infrastructure. When you come to a point that you are
having to drive the cost of the new standard higher in order to be compatible
with existing infrastructure that may or may not exist in many applications I?d
suggest that the IEEE standard should work for the long term low cost solution,
while making it technically feasible for people with the existing infrastructure
to add additional requirements to make it compatible with their existing
infrastructure. That way you do not burden the long term cost of new
installs. EG if the low cost solution needs a Tx window
of xnm to x+30nm but for compatibility with a non-IEEE standard can only be xnm
+10nm, then the IEEE spec should be xnm to x+30nm and individual vendors that
are using the non-IEEE standard can impose the tighter (subset spec) of xnm to
xnm +10nm. (This obviously only applies if the PAR and objectives
have not made compatibility with the non-IEEE standard a requirement.).
Please note my example is for illustration only the numbers in it
are not meant to apply to this specific question. From: Jim
Farmer [mailto:Jim.Farmer@xxxxxxxxxxxxx] My primary concern is
that the 1577 nm downstream wavelength is inconsistent with use of the 1550 nm
broadcast (auxiliary) wavelength. The problem is that the two wavelengths
are too close together to allow us to build economical filters at the ONU to
separate the two wavelengths. It is a little easier with the 1590 nm
wavelength, though it is still difficult. Originally I wanted to specify
the wavelength band as 1580 - 1600 nm as it was originally. But I found
that when I put in real filter characteristics, I still had an extremely narrow
transition region for the filter. So I accepted that we would have to
narrow the transmit window. I chose +/-3 nm (1587 - 1593 nm) following the
reasoning for PR(X)30. We are adding cost to the laser, but at the OLT,
which is not as cost sensitive as is the ONU. I also had to accept
that the auxiliary wavelength was limited to 1550 - 1555 nm, even though
commercial practice is to use wavelengths up to almost 1560 nm. People may
complain about this restriction, but I think in the end they will live with
it. Unfortunately I have
not been able to get quantitative information on the filter complexity - I would
like to see filter vendors jump in with comparative numbers. Some vendors
I spoke with gave me more pessimistic numbers than I used in preparing the
slides. So the application is
for anyone who wants to use the 1550 nm broadcast wavelength. This is the
only way I see to possibly make use of 1550 nm overlay practical. And it
still demands a more difficult filter than we demand currently. But
presumably advances in the state-of-the-art will made the filter practical at
some point. Thanks, jim Jim
Farmer, K4BSE From: Frank
Chang [mailto:ychang@xxxxxxxxxxx] I just reviewed this
thread, and my interpretation to Jim?s slides is that-
1)
The argument is not for
PR(X)30 as cooled TX is assumed because of tight power budget, so narrower
1577nm band considered feasible for PR(X)30. 2)
For PR10/20, possibly
uncooled optical sources are assumed, so bring about the argument that larger
wavelength band, such as wider 1590nm band, is only feasible.
To satisfy this
argument, basically call for the group to switch back to the wavelength plan
originally specified in D2.0. So actually we are re-visiting the argument the
group made during the baseline stage a year ago. Jim- Can you confirm
this is what you are looking for? As it is clear the
PR(X)30 will be assumed mainstream deployment which requires co-existence with
installed 1G version, can anybody elaborate the scenarios on how PR10/20 going
to be deployed? My question is weather PR10/20 scenarios has to use cooled or
semi-cooled optical source?
] thanks Frank C.
From: Frank
Effenberger [mailto:feffenberger@xxxxxxxxxx] To pile onto this
thread, I have a question regarding Jim Farmer?s most recent presentation and
Maurice?s support of it: Did you notice that
Jim?s presentation is asking to change the PR10/20 OLT transmitter wavelength
range to 1587 to 1593nm? (At least, that is how
I read it, but I should say that the exact numbers are not clear.)
Perhaps Jim can clarify
exactly what he is asking for? that would be helpful.
Sincerely, Frank
E> From: Marek
Hajduczenia [mailto:marek_haj@xxxxxxx] Hi Maurice,
Just following the
arguments You used in Your email: does that mean that You see PR(X)20 OLT
transmitters as uncooled devices? Are the power levels we are targeting
achievable using uncooled optics? As far as I understand, cooling is necessary
not only to keep the central wavelength within the predefined range but also
assure higher output power level. Can You comment on
this? Regards Marek From: Maurice
Reintjes [mailto:maurice.reintjes@xxxxxxxxxxxxx]
We request to make the attached
presentation during the 10GEPON meeting in Thanks, Jim Farmer, K4BSE |