Visible Light Communications: Filter-less Wavelength Division Multiplexing

In this paper, we propose a new receiver and demodulation method for use in wavelength division multiplexed visible light communications systems, utilising the natural diversity offered by photodiodes. This is based on the wavelength dependent photodiode responsivities, which lead to different signal-to-noise ratios at the receiver. Using this method, it is possible to transmit independent information using on different wavelengths but where signals occupy the same electrical frequency range and where they would, otherwise, interfere. We illustrate and experimentally demonstrate that through simple subtractions the signals can be extracted with the constellations showing Q-factors corresponding to sufficiently low bit error rates