The Absolute Wavelength Demodulation System of Large Capacity FBG Sensor Array Based on φ-OTDR Technology

The existing fiber Bragg grating (FBG) wavelength demodulation system based on Mach-Zehnder interferometer and phase sensitive optical time domain reflectometer(φ-OTDR) is limited by the system structure and working principle. It can obtain large demodulation capacity through time division multiplexing (TWD), but it can only measure the relative change of wavelength. In this paper, we design and experimentally verify a scheme for measuring the absolute wavelength of FBGs. This scheme can obtain the absolute wavelength of a large-capacity FBG sensor array without affecting the performance of the original technical indexes, and also theoretically improve the accuracy of the system. Its dynamic real-time absolute wavelength demodulation error less than 0.1pm.