Calibration process implemented in an optical calibration device comprising an optical fiber, and a first input, the first input being arranged for: - being connected to a first emitter arranged for emitting at least one optical pulse, - receiving this at least one optical pulse - injecting this at least one optical pulse towards the optical fiber the device further comprising an output arranged for: - receiving a backscattered signal generated in the optical fiber, - being connected to analysis means arranged for analyzing the backscattered signal generated in the optical fiber, the optical fiber comprising at least one event, each event being a part of the optical fiber and has at least one modified physical state or property that is different from the physical state or property of the rest of the optical fiber, the at least one event in the optical fiber being arranged for generating the backscattered signal, the device comprising means for creating different optical paths for the at least one optical pulse, the different optical paths having different lengths, each optical path passing through the at least one event the process being characterize in that: - the emitter is connected to the first input and emits the at least one optical pulse, - the analysis means are connected to the output and analyzes the backscattered signal generated by the at least one event in the optical fiber. the analysis of the backscattered signal giving a measured value of an information concerning the at least one event, the process comprising the step of comparing the measured value with a reference value of the information, if the difference between the measured value and the reference value is above a threshold value, the process comprises the step of correcting a calibration of the analysis means used for measuring the measured value the information being: - a position, a temperature, a strain, a pressure, an acoustic vibration, and/or birefringence properties of one event, and/or - an amplitude and/or frequency of the backscattered signal corresponding to one event, and/or - a spatial distance between two different events or difference of length between two of the different optical paths passing through the same event. - being connected to a first emitter arranged for emitting at least one optical pulse, - receiving this at least one optical pulse - injecting this at least one optical pulse towards the optical fiber - receiving a backscattered signal generated in the optical fiber, - being connected to analysis means arranged for analyzing the backscattered signal generated in the optical fiber, - the emitter is connected to the first input and emits the at least one optical pulse, - the analysis means are connected to the output and analyzes the backscattered signal generated by the at least one event in the optical fiber. - a position, a temperature, a strain, a pressure, an acoustic vibration, and/or birefringence properties of one event, and/or - an amplitude and/or frequency of the backscattered signal corresponding to one event, and/or - a spatial distance between two different events or difference of length between two of the different optical paths passing through the same event.