A novel distributed weak fiber Bragg gratings (FBGs) vibration sensing system has been designed to overcome the disadvantages of the conventional methods for optical fiber sensing networking, which are: low signal intensity in the usually adopted time-division multiplexing (TDM) technology, insufficient quantity of multiplexed FBGs in the wavelength-division multiplexing (WDM) technology, and that the mixed WDM/TDM technology measures only the physical parameters of the FBG locations but cannot perform distributed measurement over the whole optical fiber. This novel system determines vibration events in the optical fiber line according to the intensity variation of the interference signals between the adjacent weak FBG reflected signals and locates the vibration points accurately using the TDM technology. It has been proven by tests that this system performs vibration signal detection and demodulation in a way more convenient than the conventional methods for the optical fiber sensing system. It also measures over the whole optical fiber, therefore, distributed measurement is fulfilled, and the system locating accuracy is up to 20m, capable of detecting any signals of whose drive signals lower limit voltage is 0.2 V while the frequency range is 3Hz . 1000Hz. The system has the great practical significance and application value for perimeter surveillance systems.

提出了一种基于载波调制的光纤振动传感复用系统,其优点在于,对于感应外界扰动的不同感应光纤单元产生的干涉信号用不同频率的载波进行调制,相邻载波频率之间的频率差无需大于外界扰动引起的信号基波频率上限的两倍。各光纤感应单元形成的信号被共同的光电探测器检测后,利用信号基波来分析扰动信号的物理量,利用载波基波或谐波的边带判断感应扰动信号的光纤。