Method and sensor arrangement for measuring temperature and strain using an optical fiber embedded in a cover layer on a substrate

Abstract

In a sensor arrangement for sensing temperature and strain, an optical fiber with a Bragg grating therein is arranged on a substrate and embedded in a cover layer. The fiber is initially adhered onto an adhesive carrier, which then positions and applies the fiber onto the substrate. The fiber is point-wise fixed onto the substrate by a binder applied through holes in the adhesive carrier. Next, the carrier is stripped off to leave the fiber on the substrate. A cover layer is applied over the fiber and the substrate. Temperature and strain variations are transmitted from the cover layer into the fiber as non-circularly-symmetrical strains. The strain and temperature can be independently determined using this single sensor, by feeding quasi-depolarized light into the fiber and measuring the overlapping birefringent reflections from the Bragg grating. The full width at half maximum value indicates the temperature, while the Bragg wavelengths indicate the strain and the temperature.