Almost all modern bare metal switches are described as PHYless. What does it mean, what we need to consider?

We commonly interconnect network devices for distances below 100 meters with twisted pair or maybe 300 meters over OM3 multimode fiber for 10GBASE-SR. We can extend the span between devices to 10Km for with 10GBASE-LR, 40Km for 10GBase-ER or even 80Km for 10GBase-ZR. However, the signal path doesn’t end at the transceiver. The electronic engineer designing the circuit board must ensure that the signal received by the transceiver is transmitted to the switch ASIC (and vice versa) while maintaining signal integrity and that it a major challenge. Each of the signals traveling along the copper paths has to deal with hazards like electromagnetic interference (EMI), coupling and crosstalk, signal reflections, impedance mismatches, skew, attenuation and a host of other threats as they travel.

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