Waveguide-Type Optical Wavelength Filters

Optical communications by dense wavelength division multiplexing (DWDM or WDM), which uses a number of wavelengths and a signal on each wavelength channel for transmission, has made massive progress as a high-speed, high-capacity optical communication system for the Internet age. A crucial device in this kind of communication system is the optical wavelength filter used to separate out the wavelengths. Many different methods are used to create optical wavelength filters1). We have been focussing our developments on optical waveguide technology, due to its excellent mass producibility and optical stability.