Location of AC coupling capacitors

Question

I am trying to decide location of AC coupling capacitors between FPGA and PHY SGMII interface and datasheets of neither part has any useful information.

I've read some notes, like this one from Dr. Howard Johnson and posts here on StackExchange where people providing pros of placing AC coupling caps near a transmitter.

However I've also seen many other app notes such as this one from TI, SCAA059C that have AC coupling caps located near a receiver but not providing any reason for it. Electrically is there any benefit or reason to place AC coupling caps near a receiver?

Also, I've seen some designs where caps are placed like below. If caps on transmitter side (or receiver side) is better , why would one design like below? Could there be any practical reason why below locations might provide more benefits? .

Answer 1

While the sources cited are much more knowledgeable than I and I'm just paraphrasing much of it, I'd conclude placing the caps close to the TX pins of each chip. This minimizes both the spread of DC content and the turnaround time of reflections. If there is any connector between the two chips, it will be free of DC and thus safer wrt. accidental shorts.

Answer 2

It makes no electrical difference if the caps are chosen to have no influence on the AC signals.

If the capacitors cause a small impedance mismatch on the lines, then as long as the rest of the lines are terminated, it still makes no difference.