Measuring tip deflection in multicore fiber optic probes based on fiber segment interferometry

A multicore fiber (MCF) tactile sensor with the ability to measure its tip displacement in two lateral directions is presented. Fiber Segment Interferometry (FSI) is used to measure the differential strain between opposing cores of the MCF sensor. The all-fiber sensor is very simple to construct, using only the fiber-end Fresnel reflections of MCF sections to provide the evaluated signals. The sensor was characterized through comparison with an external interferometric reference measurement. Investigations were carried out on sensor lengths of 5 mm, 10 mm, and 15 mm, demonstrating lateral tip displacement resolutions below 1 nm/√Hz at a data rate of 5 kHz.