Systems and methods for encoding a data signal as a pulse position modulation (PPM) signal and decoding a PPM signal to output the original data signal. The method of encoding may comprise receiving an input data signal; converting the data within the input data signal to a sequence of PPM symbol values; and generating a PPM signal comprising an alternating sequence of synchronisation pulses and data pulses. The PPM signal may be generated by generating a plurality of synchronisation pulses at a fixed pulse repetition rate; and generating a sequence of data pulses with each data pulse having a time delay from a preceding synchronisation pulse, whereby the sequence of data pulses represent the sequence of PPM symbol values.