Demultiplexer for optical orthogonal frequency-division multiplexing using an optical fast-Fourier-transform circuit

An integrated-optic device for demultiplexing optical orthogonal frequency-division-multiplexed signals is described that consists of an optical fast-Fourier-transform circuit and optical gates. The fast-Fourier-transform circuit is composed of symmetrical Mach–Zehnder interferometers that are suitable for precisely adjusting filter characteristics. This device can process four or more channels with a relatively simple configuration and reduced size. An optical demultiplexer for four subcarrier channels is realized and used to demultiplex $4\times 10\mathrm{Gbit}∕\mathrm{s}$ signals.