The invention relates to an optical measurement probe for process monitoring, having a distal end, arranged in the region of a process apparatus, with a light entrance opening, and a proximal end coupled to a spectrometer, wherein a shaft comprising a light-guiding connection between the distal and proximal ends of the measurement probe is arranged between the two ends. The measurement probe is characterized in that the measurement probe has, in its distal region relative to the shaft and/or the proximal end, a reduced external diameter (FIG. 1).