DTW-based nonlinear spatial position correction in OFDR for ultra-large strain sensing up to 20000 με

In this Letter, we propose a dynamic time warping (DTW)-based nonlinear spatial position correction method for OFDR-based distributed sensing, which overcomes the fundamental failure of conventional cross-correlation-based position correction under ultra-large strain conditions (>1%). The proposed method exploits DTW's ability to establish an adaptive, point-by-point nonlinear mapping between the reference and sensing Rayleigh backscattering (RBS) spectra, thereby simultaneously compensating for localized intra-window scale distortion (spectral stretching/compression) and global inter-window positional drift. Experimental results demonstrate robust strain measurement up to 20000 με (2%) over a 50 m fiber while maintaining 2 mm spatial resolution, representing a twofold expansion of OFDR's measurable strain range. This advancement addresses the long-standing limitation of insufficient high-precision strain demodulation capability under extreme deformation conditions.