针对通过双光纤直接拉伸法获得的腰区直径达到波长甚至亚波长尺度的微纳光纤耦合器(OMC)进行了制作与实验研究；实验结果显示，当OMC 的腰区直径小于2.5 μm ，其腰区耦合功能将消失，OMC 将成为具有合束和分束功能的四端口微纳光纤(FPOM)；通过在线监测样品拉制过程、工作稳定性测试、波长扫描等实验方法，分析并界定了OMC 和FPOM 的光学特性差异；采用基于光吸收制热效应的全光调制方法，分别对OMC 和FPOM 的光调制能力进行测试分析；FPOM 具备稳定的光学传输特性，其分束比对波长、温度、传输光功率波动等物理参量不敏感，可用于微纳光子器件的集成；而经过结构优化设计的OMC 不但可以用于温度、振动等传感研究，还具备作为全光调制器的潜力。

In this paper, optical microfiber coupler (OMC) with wavelength scale of waist region which is obtained with two twisted optical fibers by direct draw method is manufactured and experimentally studied. Experimental results show that coupling capacity will almost disappear when the diameter of the waist region is less than 2.5 μm . And the OMC will serve as the four ports optical microfiber (FPOM) with the capacity of combining and splitting light. We analyze and distinguish the optical properties between OMC and FPOM by the method of online monitoring the sample drawing process，the stability measurement and the wavelength scanning. Especially, an all optical modulation method based on thermal effect caused by light absorption is adopted for measuring the optical modulation capacity of the OMC and FPOM. The stable optical transmission properties of the FPOM are verified, and the splitting ratio is almost insensitive to wavelength, temperature, transmission optical power fluctuation and other physical parameters. Such properties ensure that the FPOM can be utilized to multiplex and integrate micro photonic devices. The OMC with structure optimization can be employed to sense the temperature and vibration, as well as potentially being used as an all optical modulator.