OPTICAL FIBER GYRO

In an optical-fiber gyro for detecting a rotational angular velocity by a Sagnac phase difference of light signals propagated through an optical-fiber sensing loop, no polarizer is used, and a light source having a difference in attenuation or amplification factor between two orthogonally-polarized light streams is used. Alternatively, a light source is optically-coupled to an optical coupler for supplying two divided light signals to the sensing loop and for receiving the two light signals after their propagation through the sensing loop in an optical fiber of a predetermined length. The length of the fiber is set according to a relationship in which a distance difference determined by the predetermined length and a phase difference of two orthogonally-polarized light streams propagated through the optical fiber is greater than an interference distance of the light source.