A Hilbert-Huang transform method for vibration localization based on a dual Mach-Zehnder distributed optical fiber sensor

The dual Mach-Zehnder interferometer system has received extensive attention and applications due to its unique advantages such as simple optical path, high sensitivity and wide frequency response. However, it is very susceptible to external environmental noise and direct cross-correlation calculation method will lead to a large error. This paper proposes a data signal processing scheme based on Hilbert-Huang Transform (HHT) to realize high-precision distributed optical fiber vibration position detection. In this method, the eigenmode function is obtained by the empirical mode decomposition of the two received optical signals. The Hilbert transform and superposition of all eigenmode functions are performed to obtain the Hilbert spectrum, which can be clearly and intuitively extracted. It can accurately calculate the vibration position information by calculating the time delay caused by the vibration signal through cross-correlation. Compared with the traditional direct cross-correlation calculations, this method can effectively identify and extract the characteristic information caused by the vibration signal in the dual M-Z system. Thereby it can effectively reduce the impact of external environmental noise on the system and reduce the positioning error. This paper analyzes the related theory of the proposed method and builds a dual M-Z system for related experimental verification. The experimental results show that, compared with the traditional direct cross-correlation method, this method can effectively reduce the amount of calculation of cross-correlation data. At the same time, it can effectively improve the positioning accuracy of the vibration position. Under 10 MHz sampling rate, the positioning accuracy can reach 10 m. Therefore, the distributed optical fiber sensing technology based on the dual Mach-Zehnder interferometer system proposed in this paper has high application value.