Highly Accurate Temperature Control System Based On Matched Fiber Bragg Gratings Sensor Networks

Nowadays, sensing based on fiber Bragg grating (FBG) attracts more and more attentions due to the high precision, high speed and immunity to electromagnetic interference. Compared to the conventional fiber sensing technology (i.e. wavelength scanning), the matched FBG sensor utilizing time-division multiplexing (TDM) technique has higher demodulation rate, which can better meet the requirement of the practical applications. However, the initial wavelengths of sensing grating and matched grating would be mismatched due to the fabrication, pre-stress of installation and change of ambient temperature, as a result, the demodulation accuracy and range of the system are also degraded.In this paper, we have proposed and demonstrated a temperature controlling system based on thermoelectric cooler (TEC), in order to facilitate the system maintenance and achieve more accurate temperature control, the proposed system is designed by using modularity (i.e. one master-board and some sub-modules). The master-board could adjust the center wavelength of each reference FBG by changing the temperature of the corresponding TEC. Thus, the center wavelengths of the sensing FBG and matched FBG can be matched automatically even if the pre-stress and initial errors are presented.The system is made up of hardware, mechanical structure and software designing. Firstly, we have proposed a temperature compensation scheme based on the principle of temperature and stress of the FBG. Moreover, the hardware circuit is designed by using TEC. Afterwards, the temperature compensation scheme has been obtained by designing the mechanical structure of the system. Finally, the proposed system has been experimentally demonstrated and optimized. The results show that the temperature of the TEC can be precisely adjusted using the proposed system. In the experiment, a compensation range of0to20℃is achieved with the accuracy of less than0.2℃. In addition, temperature fluctuation is smaller than0.1℃when the system is stable. More importantly, the repeatability of the proposed system has also been obtained, which indicates the temperature compensation for the reference FBG can be realized in various environments.