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 805-nm transmitter, directed at the ceiling, emits an on-off-keyed signal having 475-mW average power. The receiver employs a 1-cm² Si p-i-n photodiode coupled to a high-index hemispherical concentrator, which is covered by an optical bandpass 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