Densely spaced wavelength division multiplexing (DS-WDM) transmission technology is one of the most promising technologies for optical high-definition (HD) CATV systems. An optical tuner is the most important key device in the DS-WDM systems. Until now, various kinds of optical tuning methods, such as a dielectric film type, an acousto-optic type, a Fabry–Perot interferometer type, and an optical waveguide type, have been proposed and studied. However, these optical tuning methods still have some problems such as fewer channels to be tuned, slow tuning response, instability during tuning, large insertion losses, and polarization dependence.

© 1991 Optical Society of America

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