Fabrication of biaxial polarization-maintaining optical fiber with ultra-low bending-dependent polarization extinction ratio deterioration

Different applications, including interferometers, gyroscopes, and frequency combs, require a single polarized light transmission by maintaining this property against the environmental perturbation. As a new type of polarization-maintaining (PM) fiber, a biaxial PM fiber was fabricated over 30 dB of high polarization extinction ratio (PER) values among two orthogonal axes over a fiber length of 110 m. The PM fiber was manufactured with a combination of an elliptical core and Panda-type geometries. The PER values were demonstrated to be preserved at harsh temperature conditions from −55 °C to +85 °C. The bending loss measurements indicate the biaxial PM fiber has ultra-low bending dependent PER deterioration (<0.5 %) at various bending diameters from 12 mm to 5 mm. The biaxial PM property was also confirmed by the group beat length measurements and found to be less than 1.5 mm at 1550 nm. The optical time-domain reflectometer (OTDR) measurements show that the optical loss of the biaxial PM fiber was below 1.5 dB/km over 3 km length. The mode-field diameter (MFD) and the numerical aperture (NA) values were also reported along two polarized axes. This novel PM fiber offers a single solution for the elliptical and Panda-type PM fibers utilized for integrated fiber-based sensors and instruments.