| 摘要 |
<p>PURPOSE: To obtain a vibration detection device by which an extremely small vibration such as a natural disaster omen vibration can be detected precisely and with high accuracy and without being influenced by a change in an environ mental condition by means of the principle of the Mach-Zehnder interferometer. CONSTITUTION: A laser beam from a laser diode 101 is spectrally diffracted and transmitted to a first optical fiber 103 and a second optical fiber 104 by an optical demultiplexer 102, and a vibration which has been applied to a sensing part 104 due to a change in an interference phenomenon appearing in a laser beam synthesized by an optical multiplexer 105 is detected. In addition, an artificial vibration is given to the first optical fiber 103 by means of an ultrasonic oscillator 110. A signal which is obtained from a first synchronous detector 116 and a light emitting current are fine modulated by a fine modulation switch 111. Thereby, on the basis of a signal which is obtained from a second synchronous detector 117, a light emitting current control part 109 is controlled by a CPU 121, and the light emitting frequency of the laser diode 101 is controlled to a frequency at which a maximum sensitivity is always obtained.</p> |
