Abstract

Optical frequency division multiplexing (FDM) is attractive because it can increase the transmission capacity and flexibility of optical network systems. Several optical multi/demultiplexers, which are key devices to FDM, are reported with an arrayed-waveguide grating type using Planar Lightwave Circuits (PLCs) and a Mach-Zehnder Interferometer type and so on. Especially, the arrayed-waveguide grating type using PLCs is more attractive because it is possible to multi/demultiplex several optical signals at a time.¹ However, a parabolic spectral response of the existing multi/demultiplexer imposes very strict wavelength control on lasers. Two approaches have been investigated in order to get a flattened wavelength response around each central wavelength.²'³ One is to employ multimode output waveguides. This approach can not be applied to the device for monomode FDM transmission systems. Another approach is to optimize respective waveguides of arrayed grating by the Fourier transfer method so as to achieve the optical field with proper amplitude and phase at the grating output. This has great attraction that an arbitrary spectral response can be theoretically realized, but needs to exactly form respective waveguides.

© 1995 IEEE