A simple quasi-distributed fiber sensing interrogation system based on random speckles is proposed for weak fiber Bragg gratings (WFBGs) in this work. Without using tunable lasers or spectrometers, a piece of multimode fiber is applied to interrogate the WFBGs relying on the wavelength sensitivity of speckles. Instead of the CCD sensor, an InGaAs quadrant detector serves as the receiver to capture the fast-changing speckle patterns. A supervised deep learning algorithm of the multilayer perceptron architecture is implemented to process speckle data and to interrogate temperature changes or dynamic strains. The proposed demodulation system is experimentally demonstrated for WFBGs with 0.1% reflectivity. The experimental results demonstrate that the new system is capable of measuring temperature change with an accuracy of 1°C and achieving dynamic frequency of 100 Hz. This speckle-based interrogation system paves a new way for distributed WFBGs sensing with a simple design.

研究了一种单光纤扫描内窥成像系统，通过直径1 mm的压电陶瓷管驱动单根光纤沿螺旋线扫描并照射目标区域，同时收集散射光来构建图像。光纤扫描运动的精确控制和成像质量息息相关，研究发现光纤由原点出发沿螺旋线扫描结束后，需要回归原点以备下一个扫描成像周期。因光纤回归的时间内无法成像，利用光纤扫描制动控制光纤快速回归原点是提高扫描成像效率的关键。同时光纤回归到原点后的残余振动大小，也对下一扫描周期的成像效果有很大影响，尤其是处于扫描起始段的中心区域。为解决上述问题，建立了单光纤扫描振动的模型，通过力学方程分析其受迫振动过程，提出了一种主动施加合适的制动信号抵消光纤惯性位移的方案，基于有限元分析的光纤制动模拟结果也证实了该主动制动的有效性。最终通过对制动控制信号的优化，光纤扫描成像效率由0.629提高为0.897，提升约1.4倍，同时中心区域的畸变消失，成像质量得到改善。该研究结果在超细多模态内窥镜、OCT以及工业内窥探测等领域都有重要的参考与应用价值。