Saturation Compensation for Visible Light Communication with Off-the-Shelf Detectors

A photodetector may get saturated if the incident optical power approaches the detector saturation threshold. In such a case, a visible light communication (VLC) system fails to recover the useful transmitted signals. We introduce a saw waveform based response characterization technique when an off-the-shelf avalanche photo-diode (APD) is deployed. Subsequently, we present two saturation compensation methods, namely the optical attenuation and gain reduction. We analytically conclude that the latter outperforms the former in terms of signal to noise ratio. Experimental results demonstrate the effectiveness of the proposed methods in improving the bit error rate (BER) and error vector magnitude (EVM) performances in the presence of strong ambient radiation and detector noise. In addition, optimization of the APD internal gain and joint employment of the two compensation methods are discussed.