基于可调谐F-P滤波器的FBG波长解调系统的动态实时校准方法

Dynamic Real-Time Calibration Method for Fiber Bragg Grating Wavelength Demodulation System Based on Tunable Fabry-Perot Filter

为减小可调谐法布里-珀罗(F-P)滤波器驱动元件的温度漂移及非线性导致的光纤布拉格光栅(FBG)波长解调误差,在分析比较串联型和并联型两种校正方案基础上,提出了一种改进型串联实时校准方法。设计了具备高热稳定性且内部温度分布均匀的参考光栅模块,通过实时测量紧贴参考光栅埋入的高精度热电阻温度值及事先标定的4支参考光栅波长与热电阻温度值对应关系,获取4个精确波长参考点,在每次扫描时实时校准可调谐F-P滤波器透射波长与驱动电压函数关系。实验结果表明采用改进的动态实时校准方法解调FBG波长的最大误差为±3 pm。与通过直接读取驱动电压确定FBG中心波长的方法相比,解调精度提高了6倍;与已报道的串联校正方法相比,解调精度提高了3倍。

In order to reduce measuremental errors of fiber Bragg grating （FBG） wavelengths resulted from the driving element of tunable Fabry- Perot （F- P） filter, which has the characteristics of temperature drift and nonlinearity, an improved dynamic real-time calibration approach is proposed after analyzing and comparing two kinds of real-time correction systems respectively with series and parallel structures. Then the real-time correction system with improved concatenation structure is investigated. The reference grating module with good thermal stability is designed to guarantee that wavelengths of four reference FBGs in the module keep constant for a long time. An accurate resistance temperature detector （RTD） is integrated into the module and clung to the reference FBGs. Before measurement, the correlation between the wavelengths of four reference FBGs and temperatures measured by RTD is calibrated. By reference points provided by referenced FBGs, the function between transmission wavelength and driving voltage of tunable F-P filter is adjusted in real time during every scanning period. The experimental results demonstrate that the maximum error is ±3 pm using the improved dynamic real- time calibration method to demodulate wavelengths of FBGs. Compared with the method to determine center wavelengths by direct acquiring driving voltages, the accuracy is enhanced 6 times. Compared with the reported method using series structure, the accuracy raises 3 times.