This study presents the successful application of smart_tendons with integrated distributed fiber optic sensors (DFOS) in post-tensioned concrete girder. Positioned in the inter-wire space, the DFOS enables continuous, high-resolution strain monitoring along the entire tendon, capturing friction losses, seating effects, and elongation with unprecedented detail. The smart_tendon enabled the spatially resolved observation of the tensioning process within the strands. Results of this experiment align well with theoretical calculations according to the standards and the European Technical Assessment (ETA). The measurements enabled the estimation of friction losses and the evaluation of losses due to wedge seating. In this experiment, friction losses were slightly higher than those predicted by the ETA, while losses due to wedge seating were slightly lower than the corresponding ETA predictions. The smart_tendon enables quality control and validation of the tensioning process and generating detailed prestressing records. By capturing structural performance from the earliest construction stage, the integration of DFOS into prestressing strands advances the capabilities of structural health monitoring (SHM) and facilitates improved safety, reliability, and long-term asset management.