Re: [8023-10GEPON] 10G-1G coexistence
Frank C.
You might find the following link interesting:
<http://www.patentstorm.us/patents/6862322-description.html>
Evidently, this typewriter company has an idea for a "switchable bandwidth
optical receiver". The basic idea is that you start with a low-rate/high
gain TIA, to which you add a FET shunt impedance. When detecting low rate
signals, you leave the TIA alone. When detecting high-rate signals, you
activate the FET so as to load down the TIA, increasing bandwidth albeit
reducing gain.
Of note, the application area in mind for this invention was classical PTP
links. To transform this to PON, there are two potential issues:
1. Burst mode: We need to change our bandwidth quickly. In my opinion, I
don't think this is a problem, because the device being used to change the
impedance is a simple electronic component - if we can't switch a FET on the
10ns timescale, then we have bigger problems.
2. Speed-sensing: In classical systems, auto-sensing/negotiation is often
the goal. But, in PON, the OLT is the master, and the OLT knows when a 1
Gb/s burst is coming in, and when a 10 Gb/s burst is coming in. So, with
that a-priori knowledge, it shouldn't be a big deal.
"What about ranging?" you might ask. Well, the simplest solution to that
would be to have two ranging opportunities, one for low speed and one for
high speed, with the TIA set appropriately. Since ranging doesn't happen
very often, it is efficient enough.
One other data-point on this area: I've heard that Calix (formerly Optical
Solutions) has a commercial system that supports both 622/155 B-PON and
2.4/1.2 G-PON in the same ONU. I'm not sure about their OLT side. Anyway,
it is an interesting approach to network evolution support, and a glimpse of
what might be possible.
Regards,
Frank E.
-----Original Message-----
From: Frank Chang [mailto:ychang@VITESSE.COM]
Sent: Sunday, January 07, 2007 2:30 AM
To: STDS-802-3-10GEPON@listserv.ieee.org
Subject: Re: [8023-10GEPON] 10G-1G coexistence
Glen;
I support the initiative to investigate this approach. One concern is that
there exist no common OLT RX o/e frond-end can handle 1G and 10G
simultaneously before able to enable one of the 2 separate sync circuits.
This is in addition to the complexity of OLT sync circuit, we need to
explore its technical feasibility as well.
Regards
-Frank
-----Original Message-----
From: Glen Kramer [mailto:glen.kramer@teknovus.com]
Sent: Friday, January 05, 2007 12:21 PM
To: STDS-802-3-10GEPON@listserv.ieee.org
Subject: [8023-10GEPON] 10G-1G coexistence
Dear Colleagues,
Based on one of straw polls taken at the November meeting, there seems to be
a strong support for using 1310 nm wavelength for upstream 10G transmission
(see Straw Poll "F" in November *unapproved* minutes). Many people have
indicated they would support this approach if coexistence can be achieved
with 1G upstream.
I believe there is a way that 10G upstream can coexist with 1G upstream,
both using 1310 nm wavelength. Please, comment on the attached slides, and
also please let me know if you'd like to be included as a supporter for this
approach.
Best regards,
Glen