WAVELENGTH FILTER AND TUNABLE FILTER

摘要

PROBLEM TO BE SOLVED: To provide a low-loss and low-cost tunable filter which has a wide tuning range and high extinction ratio.

SOLUTION: Input/output waveguides 3, 5 are connected by a connection waveguide 11 via an optical coupler 3 arranged on an input waveguide 1 at a regular intervalΔL1 and an optical coupler 7 arranged on an output waveguide 5 arranged at a regular intervalΔL2. The wavelength filter is constituted in such a manner that a plurality of optical path lengths from an incidence end 13 to an emission end 19 through respective connection waveguides are increased or decreased by a differenceΔL of the same length in sequential order starting from the path passing through the connection waveguide 11 which is closer to the incidence end 13. The refractive indices of the input waveguide 1 and the output waveguide 5 are changed by refractive index changing means 51, 53 to form the tunable filter.

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