All-optical OFDM with cyclic prefix insertion using flexible wavelength selective switch optical processing

We demonstrate that the optical Fourier transform and cyclic prefix in an all-optical OFDM transmitter can be simultaneously implemented using a liquid crystal on silicon wavelength selective switch (WSS). The design uses phase-modulated optical pulses at the inputs of the WSS; this has the advantage that the optical modulators are only sampled by the optical pulses once per data-symbol, so that the transition times between the data symbols are irrelevant to the performance of the system, allowing slow optical-modulators to be used. Furthermore, each input of the WSS can be assigned to any combination of output subcarrier frequencies, including frequencies unrelated to the modal frequencies of the comb source. This is especially useful for testing in-service ultrahigh bandwidth systems by applying additional wavelengths. As an example, we generate a 10.08 Tb/s signal and transmit along 857.4 km of fiber using 252 10-Gbaud subcarriers with a 10% cyclic prefix.We use an optically-banded digital subcarrier demultiplexer to simultaneously detect three subcarriers using a single coherent receiver.