Multichannel Fiber Bragg Grating Monitoring System Based On Dwdm

Fiber Bragg grating sensor is belonged to one of the Fiber sensors , it obtain sensing signal through the fiber Bragg wavelength which is affected by the physical quantity. As one of the wavelength optical-fiber sensor, it has powerful anti-disturbing capability and easy carrying, that is why the application of the fiber Bragg grating in sensor field has been widespread concern at home and abroad. There are some demodulation products for fiber grating sensors, which are mostly based on active demodulation technologies, and the sampling rate is between several hertz to several hundred hertz or so, can only meet the needs of static or quasi-static measurement, but is not enough to achieve the geological monitoring with high-speed and multichannel in dynamic environment. In order to adapt the requirement of dynamic measurement, increasing the sampling and transmission speed of the fiber grating demodulation is needed. As a result, the design of the high-speed fiber Bragg grating demodulation with multichannel based on DWDM is proposed in this paper. The design of optical path, circuit board and software is completed in this paper, which achieves the high-speed transmission with multichannel of fiber Bragg grating demodulation, the date processing, display, storage and analysis on computer.1,The demodulation for wavelength code in optical path is designed based on Dense Wavelength Division Multiplexing (DWDW). The performance test on DWDM is done, the experiment result shows that the effective interval in the every channel is from 1550.934nm to 1551.884nm, from 1553.280nm to 1554.205nm, from 1555.725nm to 1556.665nm and from 1558.365nm to 1559.265nm, and the sensitivity in each channel is arrived at 45dB/nm, which makes the response speed and wavelength resolution ratio rate high.2,The Complex Programmable Logic Device (CPLD) is used as the main chip in the design of the acquisition and data transmission, including the controlling of the high-speed multichannel A/D chip and the interface control circuit of USB in the project.3,The main interactive mode software is completed based on Labview 8.5, which achieves the function of the display, storage and analysis. 4,Completed encapsulation of the FBG sensors, which is packaged on the surface of the engine, and the other is packaged as the pressure sensor used for measuring the pressure of the engine.5,The monitoring system is build to analyze and research sampling rate, transmission performance, wavelength range, resolution and precision of the demodulation. The experiment results show that the sampling rate is 200 KHz for each channel, and dynamic signals on 20 KHz can be demodulated well. What is more, the relationship of surface-vibration and wavelength of the FBG sensor, and relationship of pressure of the engine and angle are researched.