In transparent dielectric bulk materials (for example silica, oxide ceramics, or polymers) 3D-dimensional waveguide structures for light with arbitrary diameter can be processed with femtosecond laser pulses. These waveguides are the basic elements for integrated photonic components and sensors, manufactured in a single (monolithic) substrate. Among others with this technique optical waveguide coupler (splitter), miniaturized integrated optical interferometers, or waveguide Bragg gratings (BGW) can be realized. BGWs are used as diffractive elements, spectral filters, or mirrors. For example, BGWs are processed in ultra-thin glass foils as sensor elements for the detection of mechanical stress or 3D-shape sensing in real-time.