Interference of selective higher-order modes in optical fibers

The interference of selective higher-order modes in optical fibers is investigated both theoretically and experimentally. It has been demonstrated that by coupling the LP01 mode in a step-index single-mode fiber (SMF) to the LP0m modes in step-index multimode fibers (MMFs) with different parameters, one can selectively generate higher-order modes and construct all-fiber interferometers. The research presented in this paper forms a basis of a new type of fiber devices with potential applications in fiber sensing, optical fiber communications, and optical signal processing.

An intra-cavity absorption fiber gas sensor based on performanceenhanced techniques

The performance of an erbium-doped fiber ring laser based intra-cavity absorption gassensor was evaluated with performance enhanced techniques. A multi-line wavelength sweep techniqueand a weighted averaging technique were proposed for better gas detection. By selecting appropriatesystem parameters, 6 strong absorption lines near 1 530 nm of C2H2 were obtained with good spectrumresolution in one scanning period. One group with higher absorption coefficients was used for relativelylow gas concentration detection and the other with lower absorption coefficients was used for relativelyhigh gas concentration. Both the groups can be used for medium gas concentration detection. For variousconcentration cases, by choosing proper absorption lines and performing weighted averaging, detectionaccuracy can be obtained over an extended detection range. The minimum detection limit could be verylow after optimization.

基于改进AdaBoost算法的可调谐F-P滤波器温漂补偿方法

针对光纤法布里珀罗可调谐滤波器(FFPTF)在环境温度变化时输出波长持续漂移,引起光纤布拉格光栅(FBG)解调不稳定的现象,提出一种基于改进AdaBoost算法的温度稳定FBG解调方法。采用AdaBoost集成学习构建可调谐滤波器的温漂模型,在迭代过程中提出基于误差率差值的弱学习器权重更新方法,以增强弱学习器权重与其预测误差之间的关联,提高多个弱学习器的集成效率。实验结果表明,传统AdaBoost补偿后可调谐滤波器在温度变化环境中的最大波长漂移为14.03 pm,而基于权重更新的AdaBoost算法补偿后最大波长漂移为4.75 pm。相比传统的基于标准具和气室的温漂补偿方法,所提补偿方法不需要添加额外元件,补偿精度高。