High sensitivity magnetic field sensor based on hybrid fiber interferometer

This paper presents and demonstrates an ultra-sensitive magnetic field sensor using a hybrid interferometer. The sensor is created by combining a Sagnac loop interferometer (SI) and a Fabry-Perot interferometer (FPI). The difference in the free spectrum ranges of the two cavities generates a Vernier effect, which amplifies the sensitivity. Experimental results indicate that the sensitivity of the single FP cavity is 25 pm/mT, while the sensitivity of the hybrid sensor is 811.53 pm/mT, which is about 32 times higher than that of a single individual FPI. The sensor can be applied in harsh environment such as mine, oil well and other fields.