Patent ID: 7043102

Claim:
A Fabry-Perot optical fiber interference sensor having a sensor part having opposed surfaces formed as parallel planes to each other in a measured clearance varied in response to physical quantities such as force, strain, pressure and temperature and the like, having a partial reflection mirror or an end surface of one optical fiber formed with a partial reflection mirror arranged in one surface side of said opposed surfaces, and having an end surface of the other optical fiber formed with a partial reflection mirror arranged in the other surface side of said opposed surfaces, in which a light of low coherence light source is guided to said the other optical fiber, either a reflected light or a transmission light modulated in wavelength in correspondence with a clearance size of said measured clearance through multiple reflection at said measured clearance is guided by the optical fiber, optical intensities in time-series corresponding to a clearance variation are attained by an optical intensity distribution sensor, either a minimum optical intensity position or a maximum optical intensity position is detected to attain said measured clearance and a value of said physical quantity is measured, wherein the same is comprised of; a wide range light source having a wide wavelength spectrum distribution acting as said low coherence light source; an optical correlation signal extracting means for extracting a desired optical correlation signal from the output signal in time-series of said optical intensity distribution sensor; and an extreme value position calculating means for attaining either a minimum position or a maximum position at said optical correlation signal in reference to the optical correlation signal outputted from said optical correlation signal extracting means.