Universite Du Quebec a Hull

Tomasz R Wolinski

Wojtek J Bock

Roland Wisniewski

A fiber-optic strain gauge manometer and a method thereof are for measuring pressure of a fluid, to be respectively connected to a light source and a measurement apparatus. The manometer comprises: a cylindrical hollow body, acting as a pressure transducer, having an inlet by which the fluid can get inside, free ends such that longitudinal and circumferential strains are generated in the hollow body by the pressure of the fluid, thereby producing a dilatation of the hollow body, and a highly birefringent optical fiber having a sensing portion bonded to the outer surface of the hollow body along a longitudinal path such that its birefringence changes when the sensing portion is subjected to the dilatation of the hollow body. A polarized light beam is generated by the light source and transmitted in a form of two polarization eigenstates each parallel to one of two parallel principal birefringence axes of the birefringent optical fiber. The state of polarization of the input light beam, being strain-modulated after a passage in the sensing portion of the birefringent optical fiber is collected by the measurement apparatus for detecting and measuring change in the birefringence as a function of the dilatation, thereby giving indication of the pressure inside the hollow body. This fiber-optic strain gauge manometer can be used for measuring pressure up to at least 100 MPa.

Fiber-optic strain gauge manometer

The method is for measurement of pressure applied to a sensing element comprising a cholesteric liquid crystal being connected to multimode optical fibers for communication with a light source and a device for measurement of light intensity. The method resides in guiding a light beam of predetermined wavelength generated by the light source toward a layer of the cholesteric liquid crystal using one of the multimode optical fibers. The light beam reflected by the layer is collected using another of the multimode optical fibers being connected to the device for measurement of light intensity. This device measures then the intensity of the reflected light beam, such that a value indicative of the pressure as a function of the measured intensity can be carried out. This method is particularly well adapted for measuring pressure up to 100 MPa with a good linear response and sensitivity for specific ranges of pressure useful in industrial applications.

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Warsaw, Poland

Tomasz R Wolinski