Vernier effect of fiber interferometer based on cascaded PANDA polarization maintaining fiber

This Letter shows the Vernier effect based on two segments of PANDA polarization maintaining fiber (PMF), whose lengths are 28 and 23 cm, respectively. The two PMFs are spliced together, and the angle between the fast axes is set to 45°. This cascaded PMF is inserted in a Sagnac loop to form an interferometer that can generate the Vernier effect. The spectrum consists of finesse fringe and envelope and realizes simultaneous measurement of strain and temperature. The envelope can provide strain and temperature sensitivities of 58.0 pm/μe and −1.05 nm/°C. The finesse fringe provides sensitivities of 5.9 pm/μe and −1.36 nm/°C.