本文讨论一种用于单模光纤模场测量的连续变孔径方法。该方法利用一个圆形光阑沿光纤轴线方向进行远场扫描,测量不同孔径角下的光功率分布,从而得出Petermann-Ⅱ定义的模场直径。与传统的变孔径测量技术相比,该方法具有测量孔径角范围宽、取样点多以及取样角度可以控制等优点,因此提高了测量精确度和拓宽了适用范围。对不同的光纤样品在1.3μm和1.55μm波长下所作的实验表明,测量不确定度小于3%。 In this paper, we discuss a continuous variable aperture method for single mode fiber mode field measurement. In this method, a circular aperture is used to scan the far field in the direction of the fiber axis, and the optical power distribution at different aperture angles is measured to obtain the mode field diameter defined by Petermann-II. Compared with the traditional variable aperture measurement technology, this method has many advantages such as wide range of measurement aperture angle, many sampling points and controllable sampling angle, which improves the measurement accuracy and broaden the scope of application. Experiments on different fiber samples at wavelengths of 1.3 and 1.55 μm showed that the measurement uncertainty was less than 3%.