Various optical circuit parts required for DWDM (Dense Wavelength DivisionMultiplexing) communication are under development as well. These include an opticalfilter module for extracting or blocking part of various multiplexed wavelength lights,and a wavelength locker for stabilizing the oscillation wavelengths of lasers. Technical Reports Development of LiNbO3 Modulators for CATV Transmission Systems Application of LN Polarization Scramblers for TV Signal Relay Systems