ABSTRACT
An arrayed-waveguide grating (AWG) is a key optical component for realizing a multi/demultiplexer, especially in dense wavelength division multiplexing systems with 16 or more wavelength channels that are arranged with a spacing of 100 GHz. The AWG is a kind of transmission grating that consists of hundreds of channel waveguides of different lengths. These waveguides are fabricated on a substrate by using planar lightwave circuit technology that includes glass film deposition, photolithography, and dry etching. The concept of the AWG, in which circular arc waveguides are concentrically arrayed in a planar waveguide substrate, was first reported by Smit in 1988. He showed that the input light beam was focused and the arrayed waveguide acted as a phased array antenna, as is well known in microwave remote sensing. He also suggested that this approach can be applied to a wavelength multi/demultiplexer. H. Takahashi described the first demultiplexing function in 1990.
