High-spatial-resolution 2D shape sensing based on OFDR using adaptive spectrum method with narrow sweep range

What we believe to be a novel wavelength shift demodulation method for optical frequency domain reflectometry (OFDR), i.e., adaptive spectrum method (ASM), was proposed and demonstrated to achieve high-spatial-resolution two-dimensional (2D) shape sensing with a narrow sweep range. The root-mean-square errors (RMSEs) of strain sections in multicore fiber (MCF) sensing cores with different local reference spectrum lengths and corresponding wavelength ranges were analyzed. Compared with traditional method, the spectral similarity of strain section was significantly improved and the strain distribution of the outer sensing cores was successfully demodulated at a spatial resolution of 2.1 mm by using ASM. Furthermore, the 2D shapes were successfully reconstructed at curvature radii of 20, 25, 30, and 50 mm, respectively. The maximum end position deviation was 6.89 mm for the MCF length of 500 mm, and the average deviation error of each reconstructed section was further analyzed. Ultimately, the ASM was deployed on the graphics processing unit (GPU) to perform parallel computation under the size of zero-padding of 1024, 2048, 4096, and 8192, respectively. Compared to serial computation on the CPU, the time consumption was reduced by a factor of 8.4 under the size of zero padding of 4096 and wavelength gap of 0.00390 nm.