Fiber optic gyroscope

A light source (10) is connected through a single mode optical fiber (51) and a coupler (52) to one end of a polarization maintaining optical fiber (54), the other end of which is connected to a polarizing optical waveguide (15) of an optical integrated circuit (14). One end of each of polarization maintaining optical fibers (55,57) are connected to two other ends of the optical waveguide (15). The polarization axis of the optical fibers (54,55,57) being coincident with the direction of the TE mode direction in the optical waveguide (15). The other ends of the optical fibers (55,57) are connected to respective ends of polarization maintaining optical fibers (56,58) with their polarization axis displaced by an angle of 45 DEG . The other ends of the optical fibers (56,58) are connected to the opposite ends of a single mode fiber optic coil (20).