Amplitude-assisted fitting demodulation for Sub-spatial-resolution field reconstruction in Raman distributed fiber optic sensing.

We propose a high-precision temperature demodulation scheme based on amplitude-assisted fitting in order to address the technical bottleneck of conventional Raman distributed fiber optic sensing system, which is constrained by the optical time-domain reflectance positioning principle and makes it challenging to achieve high-precision measurement at a sub-spatial resolution scale. In this proposed scheme, the linear relationship between the temperature, and the amplitude auxiliary parameters is established by constructing a three-dimensional mathematical model of the area value of the temperature variation curve, the amplitude auxiliary parameters and the temperature variation in the optical fiber region. The temperature measurement accuracy of the system in the sub-spatial resolution region is then greatly increased by using this numerical model to effectively correct the distorted temperature profile and reconstruct the distributed temperature field along the optical fiber. The experimental validation demonstrates that the method can increase the temperature measurement accuracy from the initial 26 °C to 2.58 °C in the sub-spatial resolution zone of 50 cm when the sensing distance is 20 km. The method innovatively overcomes the physical resolution limitation through the signal processing dimension and does not require hardware system modification or complex algorithm design, with a simple principle and strong engineering applicability, providing a new technical path for the performance optimization of the Raman distributed fiber optic sensing system.