People have made half-duplex, 2-way single-fiber links this way. With reverse-biased diodes, you are operating in photoconduction mode. If tightly-coupled to a

People have made half-duplex, 2-way single-fiber links this way. With reverse-biased diodes, you are operating in photoconduction mode. If tightly-coupled to a fiber optic, and with a quantum efficiency of say, 10%, that would mean for every 10 photons which come in, you get 1 electron charge of current flow. IIRC there are people who paint e.g. 1N4444 diodes with black paint to minimize opto-induced leakage.