Spectrometer for analyzing the spectrum of a Brillouin scattered light including input means receiving the scattered light, and selecting means for selecting and separating specific multiple frequency components of the scattered light. The selecting means has at least one main input, and at least an optical detector is coupled to the selecting means for measuring the intensity of the different frequency components and reconstructing the spectrum profile of the scattered light. The selecting means include an optical integrated circuit having at least one optical ring resonator of a first type having an input waveguide for receiving the light from the input means, a closed loop waveguide having an effective refractive index neff, and an output waveguide. The selecting means further have at least a modulator element of the effective refractive index neff coupled to the closed loop waveguide of the optical ring resonator of the first type.