| 摘要 |
PURPOSE:To enable the improvement of a detecting sensitivity and stability through elimination of a bad influence such as the dark current of a photo detector, the drift of an electric circuit, by a method wherein a phase difference, being odd-numbered times pi/2, and a phase difference, being different from the former phase difference by odd-numbered times x, are periodically switched to each other to provide it between two lights propagating in a reverse direction to each other through an optical fiber. CONSTITUTION:A phase modulator 10 serves to periodically switch light, which enters a photo detector 4 after passing through an optical fiber 3 clockwisely, and light which enters the photo detector 4 after passing through the optical fiber 3 counterclockwisely, and periodically switches a phase difference between the two lights between a first phase difference DELTApsi1=pi/2(2m-1), being odd-numbered times pi/2, and a second phase difference DELTApsi2=DELTApsi1+pi(2n-1), being different from the first phase difference DELTApsi1 by odd-numbered times x. Even if a rotary angular velocity is constant, this enables the output signal component of the photo detector to produce an alternating current, whereby an electric processing is easily conducted, and additionally, the influence such as the dark current of the detector and a DC drift at an electric system can be relieved, which results in improving a detecting sensitivity and stability. |
