Historical masonry arch bridges remain a common type of railway bridges in Germany, with many having been in service for more than 100 years. They are therefore of highest interest not only in the context of railway history, but as an essential part of the today´s infrastructure. Although most of these structures have sufficient load-bearing capacity, they are often replaced with reinforced concrete frames due to visible damage. A key factor is their spatial load-bearing behavior with significant stress redistribution potential, that current reassessment methods often fail to represent accurately. Preserving and continuing the use of arch bridges helps maintain building culture, reduce costs and contribute to climate protection. For this purpose, a series of load tests was carried out on different arch bridges in the network of Deutsche Bahn (DB), applying defined static and dynamic loads and measuring the structural behavior of the structure. The results are used to calibrate finite element models and derive recommendations for the recalculation. In addition to conventional measurement technology, distributed fiber optic sensors (DFOS) are used. The paper discusses the concept and results of the DFOS measurements for a preliminary case study, demonstrating that, with an appropriate sensor selection and installation concept, joint openings can be reliably detected under static and dynamic loading.