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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: Victor Blake
[mailto:victorblake@xxxxxxx] Mike and Marek, 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: 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 |