The fiber optic probe (7) comprises: a first optical fiber (9) to convey an electromagnetic radiation towards a measuring area at an exit end of said first optical fiber (9) a second optical fiber (11) to collect an electromagnetic radiation from said measuring area, the second optical fiber comprising an entrance end arranged in the measuring area and adjacent to the exit end of the first optical fiber. The exit end of the first optical fiber and the entrance end of the second optical fiber (11) are treated so that at least part of the electromagnetic radiation conveyed along the first optical fiber exits laterally from the first optical fiber and enters laterally in the second optical fiber. Moreover, in the measuring area an indicating material (15) is arranged, indicating a parameter to be measured with the probe. The radiation exiting from the first optical fiber passes through the indicating material so that the radiation collected by the second optical fiber is modulated by the indicating material (15).
