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

Abstract

Polarization-Maintaining Optical Fiber (PM) is a unique-designed fiber that pre-serves and utilizes the polarization state of the light transmission that is launched into it. With this aspect, our biaxial PM fiber is adequate for different applications, including interferometers, fiber optic gyroscopes (FOGs), telecommunication, and all-PM fiber lasers by maintaining single polarized light transmission against the environmental perturbation. A biaxial PM fiber, which was found to possess high polarization extinction ratio (PER) values over 30 dB among two orthogonal axes, is composed of the unique geometry that is the combination of elliptical core and Panda-type PM fibers. Even under environmental temperature conditions, from -55 °C to +85 °C, the PER values were obtained to be maintained. During the bending dependent PER measurements, it was observed that the PER values at relatively small diameters from 12 mm to 5 mm were not altered compared to the biaxial PM fibers not bent. PER deterioration was determined as 0.5%. We measured the group beat lengths which were 1.40 mm for one axes and 1.45 mm for the other at 1550 nm to confirm the biaxial PM property. The optical loss of the biaxial PM fiber was measured with an optical time-domain reflectometer (OTDR) and the loss was found to be below 1.5 dB/km for over 3 km of fiber length. Along two polarized axes, the mode field diameter (MFD) and the numerical aperture (NA) values were also determined. This novel PM fiber addresses a need for the Panda and elliptical core type (PM) fibers which are essential for integrated fiber based sensors and instruments, such as fiber optic gyroscopes.