Reducing large errors in frequency-scanned phase-sensitive optical time-domain reflectometers using phase cross correlation

The use of phase cross correlation is proposed to estimate the frequency shift of the Rayleigh intensity spectral response in frequency-scanned phase-sensitive optical time-domain reflectometry ((p-OTDR). Compared with the standard cross correlation, the proposed approach is an amplitude -unbiased technique that evenly weights all spectral samples in the cross correlation, making the frequency-shift estimation less sensitive to high-intensity Rayleigh spectral samples and reducing large estimation errors. Using a 5.63-km sensing fiber with 1-m spatial resolution, experimental results demonstrate that the proposed method highly reduces the presence of large errors in the frequency shift estimation, increasing the reliability of the distributed measurements while keeping the frequency uncertainty as low as approximately 1.0 MHz. The technique can be also used to reduce large errors in any distributed Rayleigh sensor that evaluates spectral shifts, such as polarization-resolved (p-OTDR sensors and optical frequency-domain reflectometers. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

This study proposes the use of phase cross correlation to estimate the frequency shift of the Rayleigh intensity spectral response in p-OTDR. The proposed approach is an amplitude-unbiased technique that evenly weights all spectral samples, reducing sensitivity to high-intensity Rayleigh spectral samples and minimizing estimation errors. Experimental results demonstrate that the proposed method significantly reduces large errors in frequency shift estimation, improving the reliability of distributed measurements while maintaining a low frequency uncertainty of approximately 1.0 MHz.