OPTICAL CIRCULATOR

PROBLEM TO BE SOLVED: To provide an inexpensive optical circulator easy to manufacture without complex optical axial adjustment by constituting an interference system of two directional couplers and arranging a Faraday rotator and a bire-fringent element so as to generate an optical path length difference of half a wavelength according to a light transmissive direction of light. SOLUTION: The optical circulator is arranged so that the optical path length difference between a first branched optical path 8a and a second branched optical path 8b doesn't occur, and the optical path length of the first branched optical path 8a becomes equal to the optical path length of the second branched optical path 8b by the Faraday rotator 6, a first 1/2 wavelength plate 5a and a second 1/2 wavelength plate 5b. At this time, the light made incident from an optical fiber 1 of a first directional coupler 7a is outputted from the optical fiber 3. Then, related to the light made incident from the optical fiber 3 of a second directional coupler 7b, since the optical path length difference of a 1/2 wavelength occurs always, the light made incident from the optical fiber 3 is emitted from the optical fiber 2 regardless of its polarization direction to function as the optical circulator.