Based on a dual-loop optoelectronic oscillator (OEO) with Vernier effect, a scheme of fiber Bragg grating (FBG) interrogation system with an improved scale factor has been proposed and experimentally demonstrated. Functioning as the optical carrier of the OEO, the reflection signal of two cascaded FBGs is divided into two optical beams by using a wavelength division multiplexer (WDM). The two optical beams at different wavelengths travel along single mode fibers with different lengths. After combined together by another WDM, the two optical beams go through a section of dispersion compensation fiber (DCF). The oscillating frequency shift of the OEO is determined by the overall time delay, which is affected by the wavelength change of the sensing FBG. Thus, the wavelength change of the sensing FBG can be converted into the oscillating frequency shift of the OEO. Furthermore, due to the length difference between the two optical beams, an obvious Vernier effect has been generated in the frequency response of the OEO. By detecting the frequency shift of the envelope peak of the frequency response curve, the sensitivity of the sensing interrogation can be enhanced greatly. A proof-of-concept OEO-based FBG sensor for axial strain sensing experiment is performed. The experimental results show that the sensitivity is about 0.31 KHz/μϵ for a single-loop OEO. By employing Vernier effect, the sensitivity can be improved to -11 KHz/μϵ, which is 35 times higher than that of the single-loop OEO.

中文翻译：

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基于游标效应光电振荡器的光纤布拉格光栅应变传感灵敏度增强


基于具有游标效应的双环光电振荡器（OEO），提出了一种改进比例因子的光纤布拉格光栅（FBG）询问系统方案并进行了实验证明。作为OEO的光载波，两个级联FBG的反射信号通过波分复用器（WDM）分成两束光束。不同波长的两束光束沿着不同长度的单模光纤传播。两束光束经过另一个波分复用器合束后，穿过一段色散补偿光纤（DCF）。 OEO 的振荡频移由总时间延迟决定，而总时间延迟受传感 FBG 波长变化的影响。因此，传感FBG的波长变化可以转换为OEO的振荡频移。此外，由于两个光束之间的长度差异，OEO的频率响应产生了明显的游标效应。通过检测频率响应曲线的包络峰值的频移，可以大大提高传感询问的灵敏度。进行了用于轴向应变传感实验的基于 OEO 的 FBG 传感器的概念验证。实验结果表明，单环OEO的灵敏度约为0.31 KHz/μϵ。通过游标效应，灵敏度可以提高到-11 KHz/μϵ，比单环OEO提高了35倍。