光纤激光模场及表征技术进展

在光纤通信、光纤激光器和光纤传感等领域的实际应用中，需要重点关注光纤中的模式问题。模分复用是提高光通信信息容量的有效方法，模间干涉是大多数光纤传感的基本方法，高功率光纤激光的光束质量控制的关键技术之一就是模式控制，因此，对光纤模式理论、模式产生及转换、模式表征技术开展研究具有重要的研究意义和实际应用价值。论文讨论了光纤的模式及光束质量，分析了多种模式发生及转换的方法，将模式表征方法归结为非相干、相干和低相干测量法。光纤模式表征是目前的研究热点，在多种表征方法中，空间和频谱成像法（S2）和双重傅里叶变换法（F2）具有显著的优越性，可不需要提前知道光纤的几何参数，就可获得模场分布、模式功率占比、群时延等特性。研究表明F2法更适合于表征高功率光纤激光的模场特性。

Progress on mode field distribution and characterization technology of the optical fiber laser

In fields of practical applications such as the optical fiber communications, optical fiber lasers, and optical fiber sensinIn fields of practical applications such as the optical fiber communication, the optical fiber laser, and the optical fiber sensing, it is necessary to focus on the mode problems in optical fibers. Mode division multiplexing is an effective method to improve the information capacity of optical communication. Interference between modes is the basic method for the most of optical fiber sensing. Mode controlling technique is one of the key technologies for beam quality control of high-power fiber lasers. Therefore, research on the theory of optical fiber modes, modes’ generation, modes’ conversion, and mode characterization technology are of great significance and practical application value. In this paper, we discuss the mode and beam quality of the optical fiber, analyze the methods of multiple modes’ generation and conversion, and summarize the mode characterization methods by means of incoherent, coherent and low-coherence measurement. Currently, the fiber mode characterization is a hot research topic. Among a variety of characterization methods, the spatial and spectral imaging method (S2) and the spatial and spectral double Fourier transform method (F2) have significant advantages. Without knowing the geometric parameters of the fiber in advance, we can obtain characteristics such as the mode field distribution, the mode power ratio, and the group time delay. Results indicate that the F2 method is better for characterizing mode field distributions of high-power fiber lasers.