光纤入射光束的角度和位置的变化对光纤出射光束的远场光强分布有较大影响。通过分析光纤出射光场的光强分布,研究了斜光束的偏轴角对光纤出射光场的影响。光纤耦合理论说明光纤的宏弯曲会使光纤内部模式相互耦合,根据这一原理设计一种能使光纤宏弯曲并以此来改善光纤出射场分布的机械扰模器。在实验中,对不同偏轴角入射及处于不同扰模程度的光斑进行中值滤波、高斯拟合等处理,得到光斑的径向光强分布曲线、高斯拟合度、不同出射焦比范围的能量变化等参数,以此分析机械扰模器的扰模效果。

The far-field pattern of fiber output beam changes dramatically due to different positions and angles of the input beam on fiber. This paper studies the change of the fibers output beam when the axis of input beam is shifted a small angle off the axis of optical fiber through the anlysis of the fibers output distribution. Fiber coupling theory indicates that the fiber macrobending leads to mutual coupling of fiber mode, so an improvement of fiber transmission with a mechanical scrambler which gives certain pressure to bend parts of fiber is designed. The collected output spots in different off-axis angles and scrambling degree are taken by median filtering and Gaussian fitting approaches. The scrambling effects are measured mainly through the profile of radial intensity distribution as well as its fitting degree of Gaussian distribution and the change of the energy ratio between different output focal ratio and input.