OPTICAL FIBER TYPE SENSOR

摘要

PURPOSE:To achieve an accurate detection, by making intensity modulation carrier light incident into a sensor section to detect changes in physical quantity as changes in the phase of light with the generation of a phase modulation light corresponding to the physical quantity. CONSTITUTION:A light emitting section 1 outputs an intensity modulation carrier light with an AC power source 8 which generates a frequency sufficiently higher than changes in physical quantity. The resulting output light is applied to a beam splitter 11 through a first optical fiber 2. Light branched off with the beam splitter 11 is applied to output side splitters 12 and 13 via a pi delay optical path 15 and a pi/2 delay optical path 16. The output side splitter 12 add an output light of a sensor section 3 to a carrier light delayed by pi to cancel a carrier light component contained in the output light to obtain a double side band component. The splitter 13 adds a carrier light delayed by pi/2 to the double side band component to obtain a phase modulation light. This phase modulation light is detected with a phase detector 20 provided at a light receiving section 6 to measure a physical quantity detected of the sensor 3.