Optical probe that is intended, in use, to be at least partially immersed in an aqueous medium comprising organic molecules including at least one fluorophore, comprising: A set of n sources (20, 21, 2n; 20a, 21a, 2na) of emission of UV/visible light at different wavelengths, n being an integer greater than or equal to 2, said sources being arranged to direct light towards the outside of the probe and in the aqueous medium when the probe is in use, said sources being associated with first selection means , A set of m different first bandpass filters (40, 41, 4n; 40b, 41b, 4nb), m being an integer greater than or equal to 2, associated with second selection means , arranged to receive fluorescence emissions emitted by said at least one fluorophore present in the aqueous medium in response to a light excitation originating from one of said light emission sources; A detector of fluorescence emissions filtered by a first filter selected by said second selection means associated with said set of m first filters and transmitted by said set (40, 41, 4n; 40b, 41b, 4nb) to convert said emissions into an electrical signal and A central unit designed to control the first and second selection means and to determine the concentration of said at least one fluorophore, from said electrical signal, characterized in that the probe comprises a first module and a second module linked to one another by electrical and optical connection means, the first module combining the set of the light emission sources, the first selection means and optical collection means designed to collect fluorescence emissions emitted by the aqueous medium in response to the light excitation originating from one of said light emission sources and transmit them to the second module by the optical connection means , and the second module combining the set of bandpass filters, the second selection means , the detector and the central unit , the first module being intended, in use, to be immersed in the aqueous medium. A set of n sources (20, 21, 2n; 20a, 21a, 2na) of emission of UV/visible light at different wavelengths, n being an integer greater than or equal to 2, said sources being arranged to direct light towards the outside of the probe and in the aqueous medium when the probe is in use, said sources being associated with first selection means , A set of m different first bandpass filters (40, 41, 4n; 40b, 41b, 4nb), m being an integer greater than or equal to 2, associated with second selection means , arranged to receive fluorescence emissions emitted by said at least one fluorophore present in the aqueous medium in response to a light excitation originating from one of said light emission sources; A detector of fluorescence emissions filtered by a first filter selected by said second selection means associated with said set of m first filters and transmitted by said set (40, 41, 4n; 40b, 41b, 4nb) to convert said emissions into an electrical signal and A central unit designed to control the first and second selection means and to determine the concentration of said at least one fluorophore, from said electrical signal, characterized in that the probe comprises a first module and a second module linked to one another by electrical and optical connection means, the first module combining the set of the light emission sources, the first selection means and optical collection means designed to collect fluorescence emissions emitted by the aqueous medium in response to the light excitation originating from one of said light emission sources and transmit them to the second module by the optical connection means , and the second module combining the set of bandpass filters, the second selection means , the detector and the central unit , the first module being intended, in use, to be immersed in the aqueous medium. <EOS>