RE: [EFM] RE: Wavelength allocation
Thanks for the good comments. I have a question about your last sentence:
> A minimum aim of the group could be to make provision
> for such an overlayed analogue video delivery system.
I'd like to know what you mean by "provision" here. Do you mean (a) just
leave the window open for indeterminate usage out of our scope or (b)
engineer it into the spec? I prefer (a), because writing a specific
provision for analog video overlay (b) offers these dangers:
(1) it requires extra margin in the optical power budget
(2) it eliminates 1550nm as a PMD option
(3) it would logically apply to both P2P and P2MP PMDs?
(4) increased isolation is required for analog video, which comes in very
"hot" following an EDFA. Analog video requires 40 dB isolation.
(5) Blocking filters may be required for subscriber nodes that may not use
an overlay wavelength.
(6) APC (angled connectors) would become a requirement to deal with an
analog channel sensitive to reflections.
(7) This discussion will turn to upstream return traffic from cable modems,
which can add further complications (4th wavelength, synchronization, etc).
(8) it is perhaps another sidetrack away from pure Ethernet P2P and P2MP
The point I am making is that an analog video "provision" written in a
specification for WDM overlays comes with additional system cost, complexity
and restrictions, not just component cost. But this depends on what you
mean by provision - what is your thought?
From: Thomas.Murphy@xxxxxxxxxxxx [mailto:Thomas.Murphy@xxxxxxxxxxxx]
Sent: Wednesday, July 25, 2001 9:37 AM
Subject: Re: [EFM] RE: Wavelength allocation
I agree that wavelength allocation can become a pretty
complex discussion when we start to get into wavelength grids definitions
However, I don't think we have to go this far to have some
of the benefits of an additional channel downstream. For example, integrated
components (and almost a standard) are available for separating two incoming
where one channel could carry analogue video.
The expected increase to ONU optics costs are not so high and
costs at the OLT are shared amongst all users.
A minimum aim of the group could be to make provision
for such an overlayed analogue video delivery system.