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> Do all non-optical network cards have a similar analog circuit as well? Is this generally the transceiver chip on the card? Even optical cards have this kind
by dfox 6y ago
> Do all non-optical network cards have a similar analog circuit as well? Is this generally the transceiver chip on the card?
Even optical cards have this kind of circuitry in the PHY chip. While the SFP module usually contains surprising amount of logic, most of it has to do with configuration and testing and in the end it is just an pair of LEDs with configurable analog amplifiers.
On the other hand for modern ethernet over TP (1Gbps and up) the analog interface circuitry is significantly more complex (and power hungry), because calling the thing baseband (the "base" in "1000-base-T") somewhat stretches the definition of the word. It uses various line coding and signal processing tricks to squeeze all the bandwith out of the wire.
- bogomipz 6y ago>"because calling the thing baseband (the "base" in "1000-base-T") somewhat stretches the definition of the word. It uses various line coding and signal processing tricks to squeeze all the bandwith out of the wire." Interesting. Can you elaborate on why using "base" is a stretch here? I don't think I've heard this before. It's been a while since I've looked at layer 1 but isn't Ethernet just Manchester encoding? What other signal tricks are generally used? Might you or anyone else have any good resources for Ethernet PHY circuits?
- mjevans 6y agoI vaguely recall the terms, hopefully correctly. High speed on copper, for networking anyway, has gone all analog now. That's more of a 'broad'-band (in the literal sense) than 'base'-band (in the single frequency, off/on) sense. Edit: The Wikipedia page for broadband says it better: "The key difference is that what is typically considered a broadband signal in this sense is a signal that occupies multiple (non-masking, orthogonal) passbands, thus allowing for much higher throughput over a single medium but with additional complexity in the transmitter/receiver circuitry." -- https://en.wikipedia.org/wiki/Broadband https://en.wikipedia.org/wiki/Broadband