Helical Fiber Interferometer Using Flame-Heated Treatment for Torsion Sensing Application

An interferometer using a single-mode fiber helix (SFH) was fabricated by the flame-heated treatment for torsion sensing application. For the first time to the best of our knowledge, this kind of interferometer was designed and experimentally demonstrated. By launching a linear polarized beam into the SFH, the interference was formed at the output of the structure because of the fiber bending-induced birefringence. Theoretical analysis shows that the geometrical change will bring a resonant dip wavelength shift when torsion is applied to the sensor part. Additionally, by adjusting the helix radius and pitch, the torsion sensitivity can be further optimized. From the experiment data, the torsion sensitivity reaches 1.691 nm·m /rad from -9.39 to 13.42 rad/m for the SFH with a radius of 0.89 mm and a pitch of 2.04 mm.