| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a filter in a compact size and to reduce the manufacturing cost, by composing the filter of a first and a third areas as a waveguide part in a single transmission mode and a second area as a waveguide part in a multiplex transmission mode. SOLUTION: A planar type waveguide 5 is arranged on silica glass 10 formed on a silicon substrate 15 and composed of first, second and third areas. The first and the third areas include a waveguide part in a single transmission mode and an optical signal is basically propagated in a single common transmission mode in this waveguide part. The second area includes a multiplex transmission mode or multiple waveguide part and an optical signal is basically propagated in a first transmission mode and a higher-order transmission mode. These waveguide structures are arranged between two planar type waveguides 5 not supporting the higher order mode, the unnecessary band of a wavelength of an optical signal propagating in the first transmission mode is transferred to the higher-order mode in the multiplex mode part. |
