Device for processing an optical pulse to measure the temporal contrast of this pulse, the optical pulse comprising a pedestal and a main peak on the pedestal, the device being characterised in that it comprises: - an optical separation device, comprising an input channel that receives the optical pulse, and first and second output channels to provide the main peak and at least part of the pedestal respectively, the part that is used to measure the temporal contrast, - a temporal shift device to create a temporal shift between the main peak and the part of the pedestal, - an attenuation device to attenuate the main peak such that the corresponding levels of the main peak and the part of the pedestal are of the same order of magnitude, and - an optical multiplexing device to multiplex the main peak thus attenuated and the part of the pedestal temporally shifted relative to the main peak, the contrast then being equal to the ratio of the measurement of the level of the main peak to the measurement of the level of the part of the pedestal, the levels of the main peak and the part of the pedestal being corrected by the attenuations applied to them in the processing device, in which the optical separation device comprises: - an optical division device with one input forming the input channel that receives the optical pulse, and first and second outputs to provide first and second replicas respectively of the optical pulse, the first output being connected to the first output channel, and - an optical amplitude modulation device with an input connected to the second output, and an output connected to the second output channel, designed to eliminate the main peak from the second replica and to allow only the part of the pedestal to pass when a control signal provided for this purpose is applied to it. - an optical separation device, comprising an input channel that receives the optical pulse, and first and second output channels to provide the main peak and at least part of the pedestal respectively, the part that is used to measure the temporal contrast, - a temporal shift device to create a temporal shift between the main peak and the part of the pedestal, - an attenuation device to attenuate the main peak such that the corresponding levels of the main peak and the part of the pedestal are of the same order of magnitude, and - an optical multiplexing device to multiplex the main peak thus attenuated and the part of the pedestal temporally shifted relative to the main peak, the contrast then being equal to the ratio of the measurement of the level of the main peak to the measurement of the level of the part of the pedestal, the levels of the main peak and the part of the pedestal being corrected by the attenuations applied to them in the processing device, - an optical division device with one input forming the input channel that receives the optical pulse, and first and second outputs to provide first and second replicas respectively of the optical pulse, the first output being connected to the first output channel, and - an optical amplitude modulation device with an input connected to the second output, and an output connected to the second output channel, designed to eliminate the main peak from the second replica and to allow only the part of the pedestal to pass when a control signal provided for this purpose is applied to it.