Abstract: A fiber-optic laser gyroscope having phase sensitive detecting means which can reduce rotation rate measurement errors. In the fiber-optic laser gyroscope, errors due to the relative intensity difference between two consecutive pulses, which was an error factor in rotation rate measurement through time interval measurement between two adjacent pulses, can be eliminated by having a phase sensitive detection means which may extract and detect only components having the same phase as that of a phase-modulated signal from components having the same frequency as that of a phase-modulated signal. An output from the phase sensitive detecting means has an additional characteristic of being linearly proportional to rotation rate. The fiber-optic laser gyroscope of the present invention, therefore, has a characteristic of a relatively simple signal processing compared to conventional interferometric fiber gyroscopes.

Abstract: A optical gyro can reduce the coupling loss produced when a laser beam is incident upon a photodetector and the noise generated by the laser beam returning to the laser from an external point of reflection. There is also provided a method of operating such an optical gyro. A gyro according to the invention comprises a ring resonator type semiconductor laser for having laser beams transmitted circularly in opposite directions relative to each other. The angle &agr; formed by the surface of the active layer of the semiconductor laser and the lateral surface of each of the low refractp2 ive index layers sandwiching the active layer and showing a refractive index lower than the active layer satisfies the requirement of 75°≦&agr;≦105° over the entire periphery of the low refractive index layer. The gyro detects a beat signal generated in the semiconductor laser.

Abstract: A gyro includes a laser device for generating a first and second laser beams to be propagated circuitally in opposition directions. An electric signal is taken out from the laser device. A third laser beam having an oscillation frequency different from that of the first laser beam is led to enter the laser device so as to be propagated circuitally in the same direction as the first laser beam.