Research Of Double Mach-zehnder Distributed Fiber-Optic Sensing Technology Based On FPGA

Distributed fiber-optic sensor set sensing and transmission in one,The spatial distribution information of the physical quantity and its time variation information can be detected at the same time with this technology.It's very suitable for real-time monitoring,such as oil and gas pipelines,water pipelines and bridges,dams and other large-scale,long-distance facilities.Compared to Dispersion-type or Sagnac-type fiber optic distributed sensing system,Mach-Zehnder systems with more sensitivity High,better real-time,non-blind,etc.Such as underground pipes and other weak signal detection,It has good practical value and economic value.Most Mach-Zehnder sensor systems are based on the framework of industrial computer and acquisition card.The model has the advantages of simple structure and easy implementation,However,low sampling rate,long response time of the system is one of the main causes of low spatial resolution and poor real-time.To solve the above problems,we designed a set Double Mach-Zehnder distributed optical fiber sensing system Based on FPGA.The main work are summarized below: First,from the Photoelastic effect of Fiber and interference principle,describes the working mechanism interferometric fiber-optic sensing system,and the positioning principle and time delay estimation method of Double Mach-Zehnder system are analyzed.Then design a Double Mach-Zehnder optical fiber system with Narrow linewidth lasers,Fiber Passive Components and PIN,etc.Finally FPGA as the core,with its parallel computing capabilities,combined with the characteristics of the system to optimize the correlation operation,to achieve a set of high sampling rate(20MHz),memory,parallel operation in one of the high-speed signal processing system,a single response time of less than 2 seconds(30 km detection range of circumstances).Combined with the various parts of the system,using a method of simulation of weak external vibration to detect system performance.The experimental results show that the system has high sensitivity and real-time performance,and the average positioning error is about 21.7 m.In summary,which is of reference value for the miniaturization and performance improvement of distributed optical fiber sensing system,which is beneficial to a wide range of engineering applications.