Above critical temperatures of about 200°C, high performance fibers may decompose causing deterioration of properties. This thesis presents Ge-based strong interference resonators as temperature sensors for high performance polymer fibers indicating excessive thermal exposure. The resonators consist of absorbing dielectrics on top of highly reflective metals. The color changes of the resonators arise from thermally induced optical property changes of the absorbing dielectric upon annealing. In this study, the top layers of the resonator consist of GST with different compositions on reflective noble metals as Au and Ag. The color was determined using reflectance measurements, while chemical composition and film thicknesses were identified by RBS and XRR-measurements, respectively. To evaluate the influence of roughness and adhesion, the resonators were deposited on to flat substrates, two-dimensional textile webs and polymer fibers. The results show an increasing color transition temperature from 100 to 400°C for higher Ge-content in the GST-system, where the color is dependent on the film thickness of the absorbing dielectric. It typically changes from purple or blue to yellow and grey upon annealing. The deposition on rough surfaces from two-dimensional textile webs and polymer fibers show no strong dependence of the color on the incident angle. Furthermore, the colors and optical transition temperatures of Ge-based resonators are observed to be similar for all substrates evaluated. Hence, the herein presented strong interference resonators show a potential as temperature sensors not only for high performance fibers, but also for direct application on two-dimensional textile webs.