基于3×3耦合器的光纤光栅激光传感系统波长解调方案的改进

Improvement of Wavelength Interrogation for Fiber Bragg Grating Laser Sensor System Based on 3×3 Couplers

采用3×3耦合器的光纤光栅激光传感系统(FBGLS)的波长解调结果依赖于3×3耦合器的物理特性,解调结果会因3×3耦合器三路输出的直流项、干涉条纹可见度和相位差参数的不稳定而发生一定程度的失真。理论推导给出了标定参数的方法并实现了计算机编程,能够在较大信号时实时给出标定结果,同时给出了相应的解调方案。计算机模拟发现采用上述方法消除了由3×3耦合器三路输出的参数不稳定带来的谐波,实验中解调结果的对比表明该方法带来一定程度的改善,和标准参考传感器测量结果有很高的相关性,此外基于该解调方案的光纤光栅激光传感系统具有较高的分辨率、动态范围和线性度。

The wavelength demodulation of fiber Bragg grating laser sensor （FBGLS） system with 3 × 3 couplers depend on the physical characteristics of the 3 × 3 couplers. The demodulated results will distort to some extent due to the instability of the parameters in the three outputs of 3 × 3 couplers including the direct current （DC） component, the fringe visibility of interferometer and the phase difference. A method of measuring the above parameters is given and applied in the computer programming so as to measure the parameters in real time under large signals, at the same time corresponding demodulation method is also introduced. The computer simulation shows thai with the proposed method the appearance of harmonics caused by the instability of the parameters in the three outputs of 3 × 3 couplers is eliminated. The comparison of the experimentally demodulated results also shows that with the proposed method the harmonics have been reduced and the demodulated results have high correlation coefficients with the reference sensor. Besides, high resolution, dynamic range and linearity of the demodulated results are given in the experiment by using the proposed method.