50-MB/S DIFFUSE INFRARED FREE-SPACE LINK USING ON-OFF KEYING WITH DECISION-FEEDBACK EQUALIZATION

We report an experimental 50-Mb/s free-space infrared link for indoor wireless communication, which achieves low bit-error rates (BERs) in the presence of multipath distortion, shadowing, and ambient natural and artificial lighting. The eye-safe 806 nm transmitter, directed at the ceiling, emits an on-off-keyed signal having 475-mW average power. The receiver employs a 1-cm2 silicon p-i-n photodiode coupled to a high-index hemispherical concentrator, which is covered by an optical band-pass filter of 30-nm bandwidth. A decision-feedback equalizer mitigates the effect of multipath ISI. In the presence of bright skylight, the link achieves a range of 2.9 m at 10(-7) BER.