Light Emitting Diodes for intersatellite links - LEDs4ISLs
A variety of work has been done on using LEDs for short-range intersatellite links:

Other work discussing exploiting Fraunhofer lines as relatively noise-free channels for in-space links includes:

ShindaiSat was a demonstration of LED communications to ground.

Lloyd Wood (L.Wood@society.surrey.ac.uk)