Fiber Bragg gratings are particularly suitable for measuring strain. Currently such a single parameter measurement is difficult to implement, since cross-sensitivity to temperature compels the use of an additional temperature reference - e.g., strain-inactive fiber Bragg grating. A passive athermal fiber Bragg grating strain gauge would render unnecessary the measurement of temperature. In line with this, a gauge design for fiber Bragg gratings that enables strain measurements to be performed while canceling temperature sensitivity is disclosed. The proposed design is based on a structure (2, 3) optionally composed of a single material that defines a length ratio that allows the adjustment of the temperature sensitivity of the fiber Bragg grating (1) to zero, providing athermal operation of the strain gauge. In a further embodiment, the proposed passive athermal scheme can be designed to also compensate for structural material thermal expansion, enabling load-induced strain-components to be measured.
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