The study on the novel distributed vibration sensing system based on the weak fiber Bragg gratings

摘要

A novel vibration sensing system based on the distributed weak fiber Bragg gratings has been demonstrated which can solve the drawbacks of the conventional methods used in optical fiber sensing networking, such as the insufficient quantity of multiplexed fiber Bragg gratings in the wavelength-division multiplexing systems, low signal intensity in the conventional time-division multiplexing systems. By mixing wavelength- division multiplexing technology and the time-division multiplexing technology, the physical parameters of the fiber Bragg grating locations can be measured but the distributed measurement along the whole optical fiber cannot be realized. The proposed novel sensing system detects the vibration events along the optical fiber link according to the signal's intensity interference variation caused by the reflected signals with the adjacent weak fiber Bragg gratings. The position of the vibration events can be accurately determined by using time- division multiplexing technology. The experimental results verify that this novel system is more convenient to realize vibration detection and demodulation along the whole optical fiber than before, and the system locating accuracy can be up to 20.5 m, with the capability of detecting various signals with the 0.2 V of the driven signals bottom limit voltage and the frequency range from 3 to 1000 Hz.