In the medical field of laser light application detector systems are required for measuring the light power applied to the tissue and monitoring instabilities caused by the delivery system during the application of the laser light. An isotropic detector was developed consisting of a fiber tip molded to a sphere and covered with diffuse backscattering layers. The homogeneity of the isotropic detection is 85-90% in an angular field of ±160°C. Additionally a monitoring device has been developed which consists of a darkened chamber holding a part of the fiber bent to a curve. Integrated photodiodes detect the photons 'stepping' out of the fiber. Defects of the fiber, the fiber tip, changes in the medium around the fiber tip, and variations of the laser output have influences on the detector signal. Both devices could be useful in evaluating an exact dosimetry for light.