| Summary: | 碩士 === 國立嘉義大學 === 電子物理學系研究所 === 99 === In this study, we use a wavelength-tunable single-mode diode laser for the light source. We first direct the laser into a high-speed rotating diffuser to reduce the degree of coherence. The design not only can reduce the optical instability induced by the feedback of the reflected light at the fiber endface to the diode laser, but also can help us obtain more clear fiber cross-sectional images, which can be used to perform the characterization of optical fibers more precisely. Then we use a collimating objective lens and a focusing objective lens to couple the light into a birefringent fiber, and take the output light from the fiber endface using an imaging objective lens and a CCD camera. By adjusting the drive current of the laser diode, we can obtain a variety of output wavelengths successively. Through analyzing the optical intensities of the fiber core in the fiber cross-sectional images with orthogonally polarized light under each wavelength, we can calculate the difference of refractive index between the fast and slow axes of a birefringent optical fiber. In addition, we use the same experimental configuration to explore the variation of the index difference between the fast and slow axes of an optical fiber that is subject to varied bending stress.
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