OT: Re: How does gigabit ethernet work?

From: Eric Smith <eric_at_brouhaha.com>
Date: Thu Feb 11 17:40:50 1999

Arfon Gryffydd <arfonrg_at_texas.net> wrote:n
> Well, within a cable signal, it's analog (you can therefore relate that to
> a parallel digital signal), it's also multiplex using different frequencies...
> So, I assume that the answer is, gigabit ethernet uses some local
> oscillators and modulates a butt-ton of frequencies using many parallel
> bits. That would be the closest correlation to how cable TV works.

No. What you describe is a broadband network. AFAIK, gigabit ethernet over
copper still uses baseband techniques.

However, it's not accurate to characterize the difference between baseband and
broadband as digital vs. analog. A high-frequency signal on a cable is
*always* an analog signal. Cables won't pass digital signals. If you put in
a square wave at one end, you don't get a square wave at the other. For
sufficiently low frequencies on suitably terminated cable, you may get a
good enough approximation of a square wave. But this doesn't scale up
to very high frequencies. So usually the waveform driven into the cable
(and expected at the other end) is a carefully engineered analog signal.
It is the job of the transceiver to generate that analog signal at the
transmitting end, and recover the digital data at the receiving end.
Received on Thu Feb 11 1999 - 17:40:50 GMT

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