Silica-based planar lightwave circuits for dense WDM application

Dense wavelength-division multiplexing (WDM) is an attractive method for increasing the transmission capacity and network flexibility of optical communication systems. The optical multiplexer is a key device for such dense WDM systems. Multiplexers based on silica-based planar lightwave circuit (PLC) technology are categorized into Mach-Zehnder (MZ) interferometers and arrayed-waveguide grating (AWG) multiplexers. This paper describes recent progress on silica-based PLCs with emphasis on NTT's achievements with these devices in relation to optical dense WDM applications.