Measurement of the exit characteristics of light from optical multimode plastic fibres

Optical multimode plastic fibres are an essential part of many detectors used in modern particle physics experiments. To assure an efficient fibre readout with minimal losses of the usually small amounts of light collected and propagated inside the fibres, one has to determine and understand the light exit characteristics at the fibre end. For this purpose, two experimental setups were developed in the course of this thesis. One of these setups allows the measurement of the spatial fibre light distribution at a distance down to approximately 10 µm from the fibre end surface. The other setup is used for the examination of the fibre light output at different exiting angles. With the help of this setup, the angular light distribution for angles between 0◦ and 90◦ can be examined with an acceptance of 2◦. The design of the experimental setups as well as the measurement results for round and square multimode fibres with different numbers of claddings are presented in this thesis. It is further shown how a comparison of the measured results to simulated data obtained with a specialised toolkit for Geant4 was used to verify and improve the functionality of the simulation software.