Distributed optical sensing for 2D pressure mapping in biomedical applications

Optical Backscatter Reflectometry (OBR) is capable of converting a simple and inexpensive single mode fiber (SMF) into an effective spatially distributed sensor of temperature and strain based on the concepts of Optical Frequency Domain Reflectometry (OFDR). A 2D sensing map of applied forces over a defined surface may be created by employing different spatial configurations of SMFs. This can be beneficial in biological applications such as measuring bite force. In this paper a 2D pressure sensing map based on distributed fiber optic sensing is provided. The two dimensional technique is performed by bending the optical fiber along the surface to acquire ten lines embedded in silicone material, thereby generating a carpet of 2 by 6 cm. The highly resolved sensing map is created by spacing fiber lines 2 mm apart with a sensing range of 2 mm across the fiber. The embedded fiber detects distributed strain, which is subsequently transformed into a pressure map. The dependence of strain on the toughness of silicone material was observed. The map's pressure sensitivity coefficient has been effectively identified. The setup has been validated for surface measurement of wavelength shift values over 9 sensor carpet locations with a total of 310 sensing points. Since the sensor is embedded or attached to irregular forms and geometries, the distinctiveness of sensing surfaces allows for enhanced responsiveness to curvature due to its mechanical characteristics.