Sub-millimeter resolution and high-precision φ-OFDR using a complex-domain denoising method
Kaijun Liu, Guolu Yin, Zeheng Zhang, Zixuan Zhong, Huafeng Lu, Duidui Li, Tao Zhu
Abstract
Phase noise is one of the main obstacles to achieve high spatial resolution, high precision, and large measurement range in φ-OFDR. Here, we proposed a complex-domain denoising method to achieve unwrapping of phase signals. In this method, the wrapped phase was used to construct a complex signal, and then both real and imaginary parts are denoised by using a wavelet packet. The two sets of denoised signals are reconstructed into a complex form, allowing to obtain an unwrapped phase. Additionally, the spatial position correction algorithm addresses the phase decoherence from strain accumulation. Finally, a high numerical aperture optical fiber is used to enhance the Rayleigh scattering intensity by 15 dB. The comprehensive approach yields remarkable results: a sensing resolution of 0.89 mm, a root mean square error of 1.5 µε, and a maximum strain sensing capability of 2050 µε.