Visible light communication using colour shift keying

A method of visible light communication using color-shift keying, the method comprising:

• transmitting visible light of at least six different wavelengths from respective ones of at least six graphene-based light emitting devices, each of which has a respective peak transmission wavelength different from that of the other such devices;
• and
• receiving the visible light of at least six different wavelengths at respective ones of at least six graphene-based photodetectors, each of which has a respective peak reception wavelength corresponding to a respective one of the peak transmission wavelengths of the at least six graphene-based light emitting devices, wherein at least one of the graphene-based photodetectors comprises a phototransistor at least comprising a pair of stacked graphene monolayers;
• modulating the visible light of at least six different wavelengths before its transmission using color shift keying to encode information;
• demodulating an electrical signal output by the graphene-based photodetectors to decode the information encoded in the visible light using color shift keying and received by the graphene-based photodetectors;
• and
• tuning the peak transmission wavelength of at least one of the graphene-based light emitting devices using gate voltage tuning.