HIGH SPEED BROADBAND WAVELENGTH TUNABLE FILTER AND FILTERING METHOD WITH ENHANCED STABILITY AGAINST ENVIRONMENTS

PURPOSE: A high speed broadband wavelength tunable filter and a filtering method thereof are provided to obtain a wider wavelength tunable band than a voltage signal frequency by changing a distance difference due to a birefringence with a voltage signal applied to an optical phase modulator. CONSTITUTION: A polarizer(111) receives light with polarization and outputs input light corresponding to the light with polarization. A half wave plate(114) changes the mode of input light. An optical coupler(113) divides optical power of the input light with a preset ratio and transmits the divided optical power. An optical phase modulator(115) changes the phase of the input light. A polarized beam splatter(112) transmits the input light transmitted from the polarizer to the optical coupler. A first optical path(122,123,124) connects the half wave plate, the optical phase modulator, and the optical coupler with a loop type. A second optical path(121,125) connects the polarized beam splitter and the optical coupler with a loop type.