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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 |