Applications of holographic devices for optical communications

In this paper, the applications of holographic devices for optical communications are reviewed and discussed. In dense wavelength division multiplexing (DWDM) optical communication systems, holographic devices have some potential applications to satisfy the complex requirements of the systems. We explain recent accomplishment in this field using holographic gratings (HGs) recorded in a photorefractive crystal or a photopolymer. General properties of the HG as a filter are reviewed. We note that the photopolymer HG can be used as a wavelength demultiplexer in DWDM system. It uses spatial dispersion properties of diffraction grating, which provides wavelength-dependent diffraction angle change to separate the multiplexed wavelength channels. The HG device has inherent advantages compared to the other device technologies. As specific applications of the device, we propose chromatic dispersion management of the multiple channel wavelength demultiplexer, channel wavelength tuning of the device output, and double band demultiplexer using superposed HGs. Also, we discuss optical signal routing using computer-generated holograms (CGHs) on a phase spatial light modulator. We expect that these HG devices and CGH system can exploit phase control, tunability, multiplexing and dynamic imaging control of holograms to cope with various DWDM system requirements.