基于特种光纤微结构的光纤模式耦合器件研究

The specialty fiber mode coupling device is a novel passive fiber device that fabricated in the specialty fibers with in-fiber micro-structure and special fiber doping by the plused laser. We propose the fabrication of the few mode fibers with the specially designed micro-structure and fiber doping. The refractive index modulation can be induced in the different area of the fiber by the pulsed laser, which changes the characteristics of fiber mode coupling. The high efficiency core mode coupling can be achieved. The theoretical model and numerical simulation will be compared with the experimental results to reveal the physical mechanism of the laser induced refractive index modulation. The mode coupling characteristics can be investigated experimentally by measuring the spectra, mode field distribution and refractive index distribution of the device. Based on the theoretical and experimental results, the fabrication of the specialty fiber and the laser writing of the device can be improved to increase the efficiency of the mode coupling. The mode coupling among different fiber modes can be realized and controlled. This kind of micro-structure fiber mode coupling device could have potential applications in the field of the novel multi-mode space-division-multiplexing optical communication systems and novel optical fiber sensors.

特种光纤微结构模式耦合器件是基于特种光纤微结构，结合脉冲激光诱导折射率调制技术而制备的一种新型光纤无源器件，项目建议研究制备具有光纤微结构与特殊掺杂的少模特种光纤，利用脉冲激光在光纤不同区域诱导折射率变化，从而改变光纤的模式耦合特性，实现不同纤芯模式之间的高效率耦合。将结合理论建模与数值模拟，实验研究激光引起光纤折射率调制的物理机理，器件的模式耦合特性则通过对其光谱、模场分布和折射率分布的测量进行实验研究，基于理论和实验对比研究的结果，将改进特种光纤的制备参数和激光写入方法，从而提高器件的模式耦合效率，实现模式耦合的灵活控制。这种光纤微结构模式耦合器件在新型的多模光纤空分复用光通信系统与新型的光纤传感器等领域有潜在的应用前景。

长周期光纤光栅是通过激光诱导折射率调制而制备的一种新型光纤无源器件，在光纤通信与光纤传感中有广泛的应用。本项目利用二氧化碳激光在少模光纤中成功制备长周期光栅，利用脉冲激光在光纤不同区域诱导折射率变化，从而改变光纤的模式耦合特性，实验研究了少模光纤长周期光栅的透射光谱、偏振、传感和模式耦合特性，实现了光纤纤芯模式之间的高效率耦合，并实现了光纤轨道角动量模式的产生和转换。通过调节光纤旋转与激光扫描，成功制备了螺旋光纤长周期光栅，在光纤中形成螺旋形的折射率调制，实验测量了螺旋长周期光栅的传感特性和模式耦合特性，实现了光纤轨道角动量模式的转换。结合理论建模与数值模拟，实验研究了激光引起光纤折射率调制的物理机理，器件的模式耦合特性则通过对所制备光栅的透射光谱、模场分布和折射率分布的测量进行了实验研究。这种少模光纤模式耦合器件在新型的多模光纤空分复用光通信系统与新型的高灵敏度光纤传感器等领域有潜在的应用前景。