用3×3耦合器的干涉仪直接解调光纤光栅传感器的信号

为了简单直接地解调出光纤光栅的波长移动 ,提出了另外一种非平衡马赫曾德尔干涉仪的直接解调技术。用一只 2× 2耦合器和一只 3× 3耦合器组成非平衡的马赫曾德尔光纤干涉仪 ,作为光纤光栅的波长移动解调器。解调器输出的 3路信号 ,互成 12 0°相位差。通过对 3路输出信号计算的方法 ,就可以直接解调出光纤光栅的波长移动。将 3路信号采集送入计算机 ,用软件实现了信号的解调。测量结果表明 ,在干涉仪两臂长度相关 5mm时 ,测量动态应变的分辨率达到了 0 5 1nε/Hz1/2 。还得到了输出信号的频谱和输入输出信号的关系。

Direct Demodulation for Signal from Fiber Grating Sensors by Interferometer Based on 3×3 Coupler

To demodulate wavelength shift of fiber Bragg grating, a new direct-demodulation technique is demonstrated. An unbalanced fiber Mach-Zehnder interferometer comprising a 2×2 coupler and a 3×3 coupler is used as wavelength discriminator for fiber grating, 120° phase difference between the three outputs of interferometer. The wavelength shift of fiber grating can be demodulated directly by calculating three outputs of interferometer. Demodulation is fulfilled by software when signals are sampled and inputted into computer. The minimum detectable dynamic strain of 0.51 nε/Hz1/2 can be achieved when the unbalanced length of the beams is 5 mm. The spectra of the demodulated signal and the relationship between the input and output are also given.