Optical fiber sensor for measuring pressure or displacement

Abstract

The object of the invention is to offer an optical fiber sensor for measuring pressure or displacement having a simple, compact and light-weight structure, which is capable of performing high-precision range, displacement and pressure measurements over a wide range of temperatures. The optical fiber sensor has a drive control circuit 2 which controls a laser diode 1 to emit a laser beam, which is then split by an optical fiber coupler 4. An optical fiber coupler 7 directs one portion of the split laser beam to an optical fiber 10, and the other portion to an optical fiber 16. A portion of the laser beam propagating through the optical fiber 10 is reflected at the end surface 10a of the optical fiber 10 as a reference beam, while the rest of the laser beam is reflected at a peripheral portion of a diaphragm 12 to be incident upon the end surface 10a as a reflected beam. The two beams form an interference beam which is then split by the optical fiber couple.sub.r 7. In the same manner as with the optical fiber coupler 7, an optical fiber coupler 8 splits an interference beam propagating through the optical fiber 16. The interference beams are converted to electrical signals by a photoelectric converter 22, from which distances L.sub.1 and L.sub.2 are determined and the measurement pressure P is calculated by means of a calculation processing circuit 23.