Novel waveguide filter for reducing crosstalk in optical cross connection and switching in all-optical networks

A novel filter structure is presented in this paper to reduce the crosstalk in cross connection and switching in all-optical networks based on dense wavelength-division multiplexing (DWDM). Following the principle of an optical film filter, the filter is constructed by a dielectric waveguide with the waveguide boundary or the waveguide itself discontinuous in the transmitting direction. As the propagation phase constant β does not change in the wave propagating direction z, the waveguide system can be considered as a homogeneous dielectric medium with effective refractive index n_e in this direction. Because the effective refractive index n_e changes with the thickness or parameters as n_i of the waveguide at a given field mode, we arrange different n_e alternately as an optical film filter. After proving this kind of waveguide filtering properties, the design principle and an example are given, which will be very useful to reduce the crosstalk in optical cross connection and switching in all-optical networks based on DWDM. This kind of filter can be easily connected to other related components.