This Special Issue focuses on the innovative design of optical fiber sensor structures, including fiber Bragg gratings, long-period gratings, interferometric sensors, and advanced micro-structured fibers. Optical fiber sensors are renowned for their exceptional sensitivity, compactness, and ability to operate in harsh environments, making them essential in fields such as environmental monitoring, structural health diagnostics, biomedical applications, and industrial process control. It aims to provide a comprehensive collection of cutting-edge research that pushes the boundaries of fiber optic sensor technologies, integrating them with emerging trends and. Inscription of a Fibre Bragg Grating by phase mask technique In function of the targeted application, Multitel can realize different types of fibre Bragg gratings on various types of fibred by using adapted techniques: MULTITEL can develop the most adapted interrogation system for a given. Fraunhofer IPT develops fiber-optic sensors for challenging measurement tasks such as measuring the smallest of boreholes. Using fiber-integrated beam steering and shaping, individual sensors up to a diameter of 80 microns can be manufactured. In cooperation with our spin-off company Fionec GmbH.