With the recent advances in photonic integrated circuits and their use as sensor platforms, the requirements for environmental temperature stability are increasing. Substrate free miniaturized thin film filters, used for spectral filtering, multiplexing, and demultiplexing, are affected by this requirement. Therefore, we investigate the thermal behavior of optical thin films fabricated by IBS and compare coatings on glass substrates to our substrate free miniaturized integrable alternative. We determined the relative change in optical thickness for various materials during spectral transmission measurements under sample temperature variation. Additionally, we adapted a thin film simulation software to estimate the linear coefficient of thermal expansion and thermo-optic coefficient of the materials. Since the thermal behavior of coatings is influenced by thermal expansion of the underlying substrate, we also measured the thermal behavior of simultaneously fabricated substrate free miniaturized filter elements. Comparing these results allows to pre estimate the thermal stability of the filter elements.