A New Optical Waveguide for Implementation of Multi-wavelengths Narrowband Filters for DWDM Systems

We investigate the possibility of optical waveguide with multi-levels index of refraction in the core region (more than two-levels) for multi-wavelengths applications analytically and numerically. We show that with slowly varying apodization all of dense wavelength division multiplexing (DWDM) applications with 30-dB sideband suppression and insertion losses of less than 1-dB can be implemented. The coupled wave equations and coupling coefficient for general treatment and approximated cases are reviewed. The apodization functions for obtaining narrowband filtering especially for DWDM filters are determined. Also, the capability of our proposal for implementation of superimposed gratings with constant geometry and only with suitable apodization is illustrated. Finally, some DWDM filters based on our proposal are designed.