| Thread Links | Date Links | ||||
|---|---|---|---|---|---|
| Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
|
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 Dallas.
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 Ottawa. I
quote Dr. Pearson below (with his permission, I have modified his words to try
to stay within IEEE guidelines, while not changing his meaning).
Referring to Frank Effenberger's comments (added below), Dr. Pearson
writes:
"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
Sent: Thursday, November 06, 2008 3:01 PM To: STDS-802-3-10GEPON@xxxxxxxxxxxxxxxxx Subject: Re: [8023-10GEPON] FW: Downstream wavelength 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] Sent: Thursday, November 06, 2008 3:24 PM To: STDS-802-3-10GEPON@xxxxxxxxxxxxxxxxx Subject: Re: [8023-10GEPON] FW: Downstream wavelength 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] Sent: quinta-feira, 6 de Novembro de 2008 13:13 To: marek_haj@xxxxxxx; STDS-802-3-10GEPON@xxxxxxxxxxxxxxxxx Subject: RE: [8023-10GEPON] FW: Downstream wavelength 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 Dallas. We remain
concerned over the decision to drop the 1590 nm downstream band from the plan,
for reasons shown in the attached. Note that there are notes that go with
most of the slides. You can see them by going to View|Notes
Page Thanks, Jim Farmer,
K4BSE |