The present invention discloses an optical sensor device, comprising: an optical fiber; a transducer; and an intrinsic fiber optic sensor embedded in the optical fiber; wherein the transducer is arranged as to receive an input action and converting such input action into a proportional strain on the intrinsic fiber optic sensor being at least the transducer and the intrinsic fiber optic sensor enclosed by a housing being the housing filled either with a thermally-responsive substance or a pressure-responsive substance being such device characterized in that the substance is a substance whose viscosity is reduced by at least 70% upon the change from ambient conditions to working conditions.