Optical orthogonal frequency division multiplexing using time/frequency domain filtering for high spectral efficiency

摘要

We propose a novel demultiplexing technique for a high spectral efficiency in WDM systems. This method utilizes an orthogonality between modulated signals. The multiplexed signals are demultiplexed by an optical discrete Fourier transformer; which is implemented by optical couplers, delay lines, phase shifters in frequency domain, and a bit synchronization and an optical gate in time domain. This scheme permits substantial overlapping of the spectrum and can achieve the spectral efficiency up to 1 bit/s/Hz in principle. In experimental demonstration of this scheme, error-free operation was obtained with a 0.8 bit/s/Hz of spectral efficiency.