Differential Pressure Sensor using Common Optical Fiber Path

This paper presents a new approach for differential pressure sensing method utilizing wavelengths´ coded and intensity based fiber optic sensor (FOS). This sensing system consists of two wavelengths power stabilized light sources, two pressure transducers and two photodiodes, which are cascaded by optical fibers. Transducer involves reflective cavity with pressure movable and reflective diaphragm which converts the pressure change into the optical reflectance change. One of two wavelengths is reflected back from the first filter located before the first transducer. Another wavelength is from the second filter before the second transducer. The filters have cut-off wavelengths between the two bands of the lights. Therefore, the paths traversed by the two wavelengths will differ only by the twice traversing difference between two probes. Differential pressure is uniquely evaluated by comparison of two wavelengths´ outputs. In these measurements the FOS´s response for the differential pressure change is shown within 0.1 s.