Hitachi Cable, Inc.

Hitachi, Ltd.

Munehiro Akiyama

Shigeru Oho

Hiroshi Kajioka

Hisao Sonobe

Tatsuya Kumagai

Osamu Kobayashi

Keiji Abe

A phase modulated light is propagated through an optical fiber sensing loop, from which a propagated light is obtained. The propagated light is converted to an electric signal, from which a fundamental wave component and even number harmonic wave components of a phase modulating signal for the phase modulated signal are detected. In accordance with the changes of the fundamental and even number harmonic wave components, fault is detected. On the other hand, the electric signal may be integrated to provide an integrated signal. In accordance with the comparison between the integrated signal and a fault reference voltage, the fault may be detected.

Method for detecting fault of optical fiber gyro and apparatus for

A photodetector generates an electric signal by receiving a light signal which is obtained by coupling lights having propagated through an optical fiber sensing loop in clock-wise and counter clock-wise directions, and modulated in a phase modulator. The electric signal is detected in a synchronous detection circuit to generate a fundamental wave component of the phase modulation signal, a duplicate harmonic wave component, a quadruple harmonic wave component, and an orthogonal component which is obtained in accordance with a phase shift of the quadruple harmonic wave component by one quarter period.

Phase adjustable optical fiber gyro using both even order harmonics and

A signal processing circuit of an optical fiber gyro comprises a memory for storing data measured in the signal processing circuit in accordance with angular velocities applied to an optical fiber sensing loop at preparatory stage, and the applied angular velocities. In operation, the memory is accessed in accordance with data obtained in the signal processing circuit at an operation stage, so that an angular velocity is read from the memory without complicated calculation.

Optical fiber gyro with memory storing data measured under application

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Ibaraki-ken, Japan

Munehiro Akiyama