<p>The Bowden wire transmission system is known for significantly reducing the weight and size of exoskeletons. However, the friction of Bowden wire can deteriorate control effectiveness. This friction is related to curvature. In this study, a curvature-sensitive optical waveguide material is integrated into the Bowden wire transmission system to propose a non-contact closed-loop Bowden wire transmission device based on the optical transmission properties. A theoretical model for dynamic Bowden wire friction compensation is developed by detecting the light intensity signals of the optical waveguide material and the desired output tension to provide feedforward control of the input tension. The proposed control method can be fully integrated into Bowden wires without complex structures, adaptable to most Bowden wire transmissions. The closed-loop Bowden wire is deployed on an existing line-driven exoskeleton for validation experiments. Results show that after activating friction compensation, the highest peak tension error at the end of the exoskeleton joint without sensors is 3.73 N, with an 83.21 % improvement in accuracy. Muscle activation decreases by 5.5 % compared to exoskeletons worn without friction compensation.</p>