An optochemical sensor comprises a measuring element excitable by the light of an excitation light source and in contact with a medium to be measured, and a measuring arrangement including at least one excitation light source and a detector as well as a hood separating the measuring arrangement from the measuring element, wherein the excitation light source and the detector are fixed to a base plate arranged in parallel with the measuring element, the hood, the excitation light source and the detector are separated from one another by at least a portion of the material thickness of the hood, and light from the excitation light source through an optical waveguide impinges on the measuring element at such an angle that fluorescence light emitted by the measuring element impinges perpendicularly on the detector.