Femtosecond Laser Line-by-Line Inscribed Seven Core Fiber Cascaded Fabry-Perot Cavity and Its Vectorial Bending Sensing Application

Multi-core fibers have been widely used for vector-bending sensing due to their off-axis distributed cores. In contrast to vector-bending sensors based on Bragg gratings, fiber Fabry-Perot (F-P) interferometers are more advantageous due to their ease of fabrication and potential for introducing the Vernier effect to further improve sensitivity. We propose and experimentally demonstrate a cascaded Fabry-Perot (F-P) cavity vector bending sensor. From the experimental results, the sensor has a strong bending dependence with a maximum sensitivity of 123.12 pm/m(-1), and the curvature magnitude and direction can be reconstructed from the tilted wavelength shift of the asymmetric fiber-core F-P cavities.