Patent ID: 6337937
Filing Date: 2002-01-08
Classification: G02B

Abstract:
An optical filter comprising:an optical waveguide having a core region which has a predetermined refractive index, and a cladding region which is provided on an outer periphery of said core region and has a lower refractive index than said core region; a first filter region arranged at a predetermined position at least in said core region, and provided with a first long-period grating attaining an attenuation peak at a first wavelength by mode coupling, a refractive index of said first filter region varying with a first period; and a second filter region arranged at a predetermined position at least in said core region, and provided with a second long-period grating attaining an attenuation peak at a second wavelength different from said first wavelength by mode coupling, a refractive index of said second long-period grating varying with a second period; wherein the order of cladding mode in light attenuated by said first long-period grating to couple with a core mode thereof differs from the order of cladding mode in light attenuated by said second long-period grating to couple with a core mode thereof.