基于3×3耦合器的马赫-曾德尔干涉仪的光纤光栅波长解调技术

介绍了一种基于3×3和2×2光纤耦合器构成的非平衡马赫-曾德尔干涉仪的波长解调方案。理论分析和数据对比表明，相对于由两个2×2光纤耦合器构成的马赫-曾德尔干涉仪，本干涉仪具有宽谱的灵敏度、能跟踪波长的变化方向和相位展开的优点，实验方案用于测量固定在悬臂梁上的传感光纤布拉格光栅（FBG）的峰值波长变化，获得了±1pm的静态波长解调精度，在10Hz处的动态分辨率为27nε/√Hz。相位展开算法使得应变测量范围达到了2014με，对应的相位变化为3．22π。

A wavelength interrogation scheme which based on a unbalanced Mach-Zehnde interferometer (MZI) composed by a 3×3 and a 2×2 fiber coupler was introduced. Theoretical analysis and experimental data showed that compared with MZI by two 2×2 couplers, the experiment MZI has advantages of high sensitivity in wide spectral range, and possibility of tracking wavelength change direction and phase unwrapping. The experimental set-up was used to measure the peak-wavelength change of an fiber Bragg grating (FBG) strain sensor fixed on a cantilever. The static resolution of wavelength interrogation of the set-up was measured to be ±1 pm, and the dynamic resolution to be 27 nε/Hz at 10 Hz frequency; the strain range as large as 2014 με was demodulated by a phase unwrapping algorithm, corresponding to a phase shift of 3.22π.