Apparatus for absolute and spatially resolved measurement of the thermally-related absorption of a light beam in an optical fiber

The invention relates to a device (10) for absolute and spatially resolved measurement of the thermally-related absorption of a light beam (80) in an optical fiber (90) comprising a first light source (12) for generating the in the optical fiber (90) to be fed light beam ( 80), transparent one (for a measuring light beam 70) and a temperature dependent refractive index exhibiting the optical fiber (90) enclosing in the radial direction thereof over the entire circumference medium (20), a second light source (14) for generating the measurement light beam (70) and feeding it into the medium (20) in such a way that the measuring light beam (70) without intersecting with the optical fiber (90), and a detector arrangement (30) for measuring the angle by which the from the medium (20) emerging measurement light beam deviates (72) fed from the in the medium (20) measuring light beam (70).