In the course of the development of a concept for a spectrally resolving thermography diagnostic for the ITER divertor using optical fibres experimental development work has been carried out in three different areas. Firstly ZrF4 fibres and hollow fibres (silica capillaries with internal AG/AgJ coating) were tested in a Co60 irradiation facility under c irradiation up to doses of 5 kGy and 27 kGy, respectively. The ZrF4 fibres suffered more radiation induced degradation (>1 db/m) then the hollow fibres (0–0.4 db/m). Secondly multi-colour pyroreflectometry is being developed towards tokamak applicability. The emissivity and temperature of tungsten samples were measured in the range of 700–1500 C. The angular working range for off normal observation of the method was 20–30. The working distance of the method has been be increased from cm to the m range.