提出并制造一种新颖的椭圆芯中空光纤，采用热极化方法使其具有高二阶非线性，可用作相位调制器。该光纤在300 ℃温度、大于1×108 V/m强电场和9 cm有效电极长度条件下热极化30 min后，产生大的线性电光相移。基于双椭圆芯中空光纤构建一种纤内马赫曾德尔干涉仪，通过观察干涉条纹的移动来评估相移，最终得到1.16 pm/V的高二阶非线性系数和0.52 pm/V的线性电光系数。该技术具有简单、灵活的特点，可以用来制作高电光系数器件，降低制作成本，并能进一步提高全光纤器件的集成度。

A novel elliptical-core hollow fiber (ECHF) with high second-order nonlinearity (SON) applied in phase modulator is proposed and fabricated. A large linear electro-optic phase shift observed in the fiber has been induced by thermal poling at about 300 ℃ for 30 min with an electric field larger than 1×108 V/m and a 9-cm-length electrode. Based on ECHF an in-fiber Mach-Zehnder interferometer (MZI) is constructed, movement of interference fringe to estimate phase shift is observed. As high as 1.16 pm/V SON coefficient and 0.52 pm/V linear electro-optic (EO) coefficient are obtained. This technology is simple and versatile that can be utilized to fabricate high EO coefficient devices, which can decrease fabrication cost, and realize higher integration level of all fiber devices.