Optical fiber gyro

An optical fiber gyro, comprising;

• a light source for emitting a light signal;
• an optical fiber for propagating said light signal to a predetermined position, said optical fiber having a predetermined length;
• an optical coupler for receiving said light signal supplied from said optical fiber to be divided into first and second light signals, and receiving third and fourth light signals to be combined as a combined light signal;
• an optical fiber sensing loop having first and second ends, said first and second light signals being optically coupled to said first and second ends of said optical fiber sensing loop to be propagated through said optical fiber sensing loop in clockwise and counter clockwise directions and to be supplied as said third and fourth light signals from said first and second ends;
• a light receiver for receiving said combined light signal supplied from said optical fiber to be converted into an electric signal, said combined light signal being transmitted through said light source, and said light receiver being positioned behind said light source;
• and
• a signal processing circuit for processing said electric signal to provide a rotation angular velocity of a rotating member in accordance with a phase difference of said third and forth light signals, said rotating member being loaded with said optical fiber sensing loop;
• wherein said predetermined length of said optical fiber is set to meet a relation in which a distance difference determined by said predetermined length and a phase difference of two orthogonally polarized lights propagated through said optical fiber is greater than an interference distance of said light source;
• and
• said optical fiber and said optical fiber sensing loop are of a polarization plane maintaining optical fiber.