[fecal_henge]

SerDes is already frequently parallelised. The difference is you never expect the edges or even the entire bits to arrive at the same time. You design your systems to recover timing per link so the skew doesnt become the constraint on the line rate.

[bgnn]

one can implement SerDes at any point of the electro-optical boundary. For example, if we have 1 Tbps incoming NRZ data from the fiber, and the CMOS technology at hand only allows 10 GHz clock speed for the slicers, one can have 100x receivers (photodiode, TIA, slicer), or 1x photodiode, 100x TIA + slicer, or 1x photodiode + TIA and 100x slicers. The most common id the last one, and it spits out 100x parallel data.

Things get interesting if the losses are high and there needs to be a DFE. This limits speed a lot, but then copper solutions moved to sending multi-bit symbols (PAM 3, 4,5,6,8,16.. ) which can also be done in optical domain. One can even send multiple wavelengths in optical domain, so there are ways to boost the baud rate without requiring high clock frequencies.