Birefringent Interferometer Cascaded With PM-FBG for Multi-Parameter Testing

In this paper, a structure depending on a birefringent interferometer (BFI) cascaded with polarization-maintaining FBG (PM-FBG) is proposed and experimentally demonstrated. Two different kinds of PM optical fiber spliced with a 45° rotation between their polarization axes composed of BFI. The dip wavelength shifts have a function with the surrounding strain and temperature. To detect the surrounding refractive index (RI), the Michelson interferometer (MI) implemented with waist-enlarged technology is also proposed. Though evaluating the quality of the birefringent interferometric, MI, and PM-FBG signals as a function of temperature, strain, and refraction index, it has been found that this compact sensor can detect these three parameters. We expect this novel sensor to be of great value for bright structural applications.