Wavelength-division-multiplexed and identical -weak Bragg grating arrays in multicore fiber for single-channel OFDR shape sensing

The multicore fiber shape sensing technique faces challenges in system complexity and cost due to the need for simultaneous measurement of multiple cores, and the massive data volume increases computation time. In this work, we report a single-channel optical frequency domain reflectometry (OFDR) shape sensing method using wavelength-division-multiplexed (WDM) and identical-weak (IW) Bragg grating arrays in multicore fiber. The WDM grating arrays are multiplexed in seven cores and IW grating arrays are connected in series within each core. This method enables synchronous strain measurement of seven cores through a single scan and without extra optical device. In experiments, we fabricated 1.5mm-long gratings in all seven cores using femtosecond laser direct writing, achieving strain measurement accuracy below 6 µε with 1.5 mm spatial resolution. We also demonstrate fiber shape reconstruction at a length of 0.40 m, with the maximum shape reconstruction errors per unit length are 2.61% and 2.75% for 2D and 3D shape, respectively. Furthermore, we conducted a proof-of-concept experiment by integrating the shape-sensing fiber into a medical catheter and navigating through an arterial model, successfully reconstructing the catheter's 3D shape within the model and validate its potential for endovascular interventions.