Temporal Filtering Technique Using Time Lenses for Optical Transmission Systems

An optical signal processing scheme using time lenses in a 4-f configuration for optical communication systems is discussed. The first time lens combined with a dispersive element such as an optical fiber produces the Fourier transform of the input signal, and the second time lens combined with a dispersive element placed after the temporal filter produces the inverse Fourier transformation. Typically, in an optical signal processing scheme based on space/time lens, the signal at the output is space/time reversed because of the direct Fourier transformation after the spatial/temporal filter, which is undesirable for a practical optical communication system. This chapter discusses various schemes to implement the direct and inverse Fourier transformation. Three applications using the time lens-based scheme, a demultiplexer for wavelength division multiplexing systems, a higher-order dispersion compensator, and an optical orthogonal frequency-division multiplexing system, are addressed and numerically implemented.