Re: AW: [EFM-P2MP] RE: [EFM] T.V. broadcast / unicast
Thomas,
Wavelength overlays were the first method we looked at when designing our
reference model for FTTH with video service included. After more careful
research, we found that the use of an analog video overlay incur in some
penalties, which may or not be relevant depending on the cost of the
components involved. Analog signal is prone to interference by reflected
signals, and thus have to use non-reflective (high reverse path loss)
connectors. The power budget is also significantly higher, pointing out the
need for amplifiers. Most of these problems can be solved by careful
engineering, but are important issues anyway.
Please note that I'm not against wavelength overlays; I strongly believe
that they are a very important part of the proposal for optical access
networks. I'm only pointing out some of the problems that happen when you
mix two completely different modulations (analog video x digital data) over
the same medium. Other situations, such as two (or more) digital carriers,
are not subject to the same set of problems.
Carlos Ribeiro
CTBC Telecom