how layout high speed pulse PCB traces?
@peufeu traces into 6n137 opto-coupler and traces from output of it to the fpga. typical Tplh 48ns. – oppo 8 mins ago 


\$\frac1{48\,\text{ns}}\approx \frac1{50}\,\text{GHz}=20\,\text{MHz}\$, take this times 5 to get basically all relevant sidelobes of the sinc spectrum of a rectangular signal, get 100 MHz; so no high frequency or high speed signal in the modern sense.

For 100 MHz, it's still good practice to make sure your trace is constant width, and runs over a ground plane, and isn't directly near sensitive other lines.

Without knowing your circuit, it's hard to advice, but considering the input side of your optocoupler has a typical forward current of 20mA, I'd argue that unless you have an extremely low impedance signal source, no further load matching needs to be done.

Note: 20mA is a lot for a 48ns pulse to ask for from a simple output driver, so make sure the driven pins of the FPGA are spec'ed to deliver that much current, or find a less current-hungry optocoupler (still check!).