保偏光纤模场直径和数值孔径测试研究

基于光纤测量远场法原理测量光纤远场光强分布。通过改进远场法得到光纤的远场光强分布后,同时计算得到保偏光子晶体光纤的模场直径和数值孔径,使测量装置实现集成化和简便化。通过光束测试仪测量光纤的出射光强分布,光束测试仪测量的是光纤中心最大光强点的两个垂直方向上的光强分布。保偏光子晶体光纤的出射光斑是椭圆的,每个方向的模场直径、数值孔径分布并不相同。传统的测试方法不能解决这个问题。通过旋转光纤测量光纤各个方向上的光强分布,然后计算各个方向上的模场直径,最后通过拟合各个方向上的模场直径得到保偏光子晶体光纤椭圆形的模场分布。实验测得保偏光子晶体光纤椭圆光斑长短轴的模场直径分别为7.5μm和4.2μm,数值孔径分别为0.159和0.276。

Test method of mode field diameter and numerical aperture of polarization-maintaining optical fiber mode field

Based on the principle of the far field method for optical fiber measurement,the light intensity distribution in the far field of the optical fiber is measured.The far-field intensity distribution of the optical fiber is obtained,and the mode field diameter and the numerical aperture of the polarization maintaining photonic crystal fiber are calculated by the modified far field method.In this way,the measuring device can be integrated and simplified.We measured the light intensity distribution of optical fiber through a beamscan.Beamscan measured optical fiber in two perpendicular directions of maximum intensity.Traditional test methods can not solve this problem.By rotating the optical fiber,measuring the light intensity distribution of optical fiber in all directions,and then calculating the mode field diameter in each direction,we obtained the elliptical mode field distribution after fitting the mode field diameter of polarization maintaining photonic crystal fiber.The mode field diameters of the long and short axes of the elliptical spot of the polarization maintaining photonic crystal fiber are measured to be 7.5μm and 4.2 μm,respectively,and the numerical apertures are 0.159 and 0.276,respectively.