Photosensitivities in germanium-doped planar waveguides and dye-doped polymer optical fibres

We present an improved design approach for N×N silica-based multimode interference (MMI) devices. By this approach, we could determine a well-defined range of the length of the multimode section that would produce optimal device performance. The range is linked to the propagation constant spacing of fundamental and higher order modes of the multimode waveguide. Related design principles and issues of silica-based MMI devices will be discussed