Adicore has what appears to me to be an extremely long selection of bandwith 20 ma leds. Are you sure you can't find low power ones that fit your needs? I find Adicore to be quick to ship and low in price.Those were the only one's I could find capable of producing the range of acceptable wavelengths (roughly 660 nm up to just short of near infrared). Power supply current limit is basically 20-30 ma. LED will essentially provide three functions: transmission, detection, and illumination. The first two will require very little current to operate, the illumination will consume the vast majority of the circuit's power.
Okay, thanks, that's a relief to hear. I can just experiment with the frequency setting, but do you off chance happen to have any idea what sort of frequencies we're talking about here? I realize of course that it may be different for various wavelengths, but a ball park guess might be helpful in any case.