The invention relates to an optical sensor device comprising a reference body, an optical fiber including an intrinsic fiber optic sensor, and a hydraulic transmission system. The hydraulic transmission system is connected to the reference body such that an input portion and an output portion are movable with respect to the reference body. The optical fiber is connected with a first connecting portion to the output portion of the hydraulic transmission system and with a second connecting portion to an element exterior to the hydraulic transmission system. The intrinsic sensor is positioned between the first and second connecting portion. The input portion is arranged for receiving an input action and the hydraulic transmission system is arranged for converting the input action to a sensing action applied to the optical fiber by the output portion such as to modify strain in the optical fiber dependent on said input action.