A seven-core fiber torsion sensor with microcavity structure based on intensity measurement is proposed. It is composed of a seven-core fiber (SCF) and two multi-mode fibers (MMF). The first end of the SCF has a microcavity structure. Because the mode fields between the MMF and SCF do not match at the splicing point, the phenomenon of mode interference will be formed between cladding modes and core modes. Experimental results show that in a clockwise situation, the intensity of transmission spectrum increases in the torsion range of 0$\sim$70°, the torsion sensitivity is 0.098 dB/${}^{\circ }$. And in a counterclockwise situation, the intensity of transmission spectrum decreases, the torsion sensitivity is 0.103 dB/${}^{\circ }$. The sensor has a simple structure and easy to fabricate, so it has wide application prospects in the field of torsion sensing.

提出了一种基于强度测量的微腔结构七芯光纤扭转传感器。它由一根七芯光纤（SCF）和两根多模光纤（MMF）组成。SCF的第一端具有微腔结构。由于MMF和SCF之间的模场在熔接点不匹配，包层模和纤芯模之间会形成模干扰现象。实验结果表明，在顺时针方向的情况下，透射光谱的强度在0扭转范围内增加$～$70°，扭转灵敏度为0.098 dB/${}^{\circ }$. 在逆时针情况下，透射谱强度减小，扭转灵敏度为 0.103 dB/${}^{\circ }$. 该传感器结构简单，易于制作，在扭转传感领域具有广阔的应用前景。