Compensation for fabrication-induced center wavelength shift in a coupled waveguide type multi/demultiplexer

A new coupled waveguide type multi/demultiplexer is proposed together with a fabrication method which can compensate for the shift Deltalambda(0) in wavelength caused by fabrication errors. This waveguide formed on a low refractive index layer is embedded by a cladding layer with index n(c). In this structure, Deltalambda(0) can be compensated for by optimizing n(c) (which is calculated by measuring the deviations from the design values for core width, core height, and waveguide separation) before cladding the waveguide. A cladding material with an optimum n(c) is coated on the entire waveguide including the cores.