Photo-induced birefringence in single-mode optical fiber

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Virginia Tech

Single-mode optical fiber has been widely used not only in long-haul, high speed digital communication systems but also in sensing applications because of its inherent immunity to electromagnetic interference, low transmission loss, wide bandwidth, small size, and light weight. Birefringence is an important parameter of the optical fiber, determining bandwidth in fiber optic telecommunications, and resolution in fiber optic sensors. This thesis describes and demonstrates permanent photo-induced rotation of the principal axes of birefringence in Ge-doped circular-core low-birefringence single-mode optical fiber. Light from a linearly polarized Ar⁺ laser at a wavelength of 488 nm was launched into the fiber along one of the principal axes of the initial birefringence in the fiber. Rotation of the principal axes was observed after several hours of exposure. This observation helps one to understand the mechanism of the photo-induced effects in Ge-doped optical fiber, and to discover possible ways to control the birefringence in the fiber by means of photo exposure.