Demonstration of channel-spacing-tunable demultiplexing of optical orthogonal-frequency-division-multiplexed subcarriers utilizing reconfigurable all-optical discrete Fourier transform

We experimentally demonstrate a tunable and reconfigurable optical discrete Fourier transform (DFT) to demultiplex orthogonal-frequency-division-multiplexed subcarriers with 2/3/4 subcarriers at 20/40  GHz frequency spacing. An average power penalty of ∼5  dB (∼3.5) at bit error ratio of 10−9 is achieved for 4×20  Gbit/s (4×10  Gbit/s) OFDM signal with 20 GHz frequency spacing.