Optical fiber sensor having function of compensating for all drifting components

摘要

An optical fiber sensor, which has a detector section connected in a single optical path made of an optical-fiber cable and having a light- modulating element and an optical element connected in series. The light- modulating element has its birefringence degree changed in accordance with the physical quantity to be sensed, thereby to modulate the polarization state of the physical quantity. The optical element converts the polarization state of the physical quantity into the intensity of light. The sensor further comprises two light sources, which apply two light beams having different wavelengths &lgr;.sub.1 and &lgr;. sub. 2 to one end of the optical path. The intensities P.sub.1 and P.sub. 2 of the beams of the wavelengths &lgr;.sub.1 and &lgr;.sub.2, both emitted from the other end of the optical path, are detected. The intensities &lgr;.sub.1 and &lgr;.sub.2 vary in accordance with the changes in the intensity of the light emitted from the light sources, in the loss at the optical-fiber cable and the optical connector, and in the physical quantity to be detected. To obtain data free of the changes in the intensity of the light emitted from the light sources, in the loss at the optical-fiber cable and the optical connector, one type of the sensor has means for controlling one of the light sources such that the intensities P.sub.1 and P.sub.2 are at the same level, and means for detecting the intensities P.sub.01 and P.sub.02 of the light beams emitted from the two light sources and performing the calculation of (P. sub.01 -P.sub.02)/(P.sub.01 +P.sub.02).