A novel composite interferometer sensor is presented and its sensing characteristics are investigated. Based on the infiber
integrated Michelson interferometer, a quartz tube is used to encapsulate the ends of the twin-core fiber and single
mode fiber to form the dual extrinsic FP cavities. Thereby, the Michelson and FP configurations are integrated into a
single fiber, which we call it Michelson-FP composite interferometer sensor. The novel sensor can respond to the axial
strain and radial bending simultaneously. We have derived and analyzed the interferometer principle of the new structure.
The analysis results show that the interferometer sensor could be considered as the superposition of Michelson
interferometer and FP interferometer. Moreover, we establish a testing system and conduct a series of experiments to
investigate the strain and bending characteristics. We measure the reflection spectra with the spectrum analyzer. The
spectral response of the composite interferometer sensor presents two pattern fringes with different frequencies due to
the respective optical path interferometers. The experimental results indicate that the composite interferometer sensor is
very sensitive to the strain and bending characteristics, and the presented sensor has different strain and bending
sensitivity coefficients. Due to these characteristics, the presented sensor might be able to measure the strain and bending
characteristics simultaneously. In conclusion, the presented novel interferometer sensor is of compact structure, high
integration and good strain and bending sensing characteristics. Thus, many types of fiber-optic sensors may be built
based on it.