@Cd_Sharp, I tried this scenario but with a LED, an 1 ohm resistor and AMP=6V (else the light of my LED is very low), I don't see that spike.
Here are some photos (link to larger image here):
Are you sure that's not just an scope artifact because of the low frequency ?
I suggest doing the same test using a LED, check if the spike is still present. Or maybe there is something in the optocoupler's circuit provoking that spike ?
A test with a simple LED and current-sensing resistor just like I tried will clarify that spike's source.
Edit: Also try with the auto-trigger feature of the scope, if it's just an artifact this could remove it.