| An instrument measuring the distributed polarization coupling in high birefringence polarization-maintaining fiber (PMF) is developed based on white light interferometry. The instrument is used for the detection of distributed polarization mode coupling point in PMF. It can be used as an effective testing tool in PMF manufacture and applications. The performance of optical fiber polarization devices or systems can be improved significantly.Based on previous work of our lab, further study has been done in the system theory, instrumentation, experiments and applications. The relationship between external perturbations and PMF's birefringence, polarization coupling is deduced mathematically. The influence of the scheme itself, polarization modes, state of the instrument on the interference results are analyzed and a calculation method is put forward free of the system error for the obtain of coupling intensity and coupling point position. The system optics, mechanics, hardware, data processing and software had been designed and realized. When the fiber under test has no birefringence dispersion, a length of 500m PMF can been scanned with spatial resolution of 6cm and coupling intensity detection sensitivity less than–80dB. Based on the instrument, a series of applications are developed including PMF ring testing and so on.Major innovations of this dissertation:1. Based on mode coupling theory, principle of photo elastic and elasticity, a concatenation of three PMF sections is used to model the polarization coupling phenomena. It's revealed that the rotation of the principle axes of perturbed PMF is the source of polarization modes coupling. The relationship between the coupling intensity and the amplitude, direction, and the acting length on the fiber of the force is clarified. And the phenomenon is applied in the field of distributed stress sensing.2. The influence of the birefringence dispersion on polarization coupling test is illustrated for the first time. The role of birefringence dispersion is clarified theoretically and experimentally. As the increasing of fiber length, the interference packet envelope is broadened and the interference contrast becomes worse.3. The influence of exited state of polarization (SOP) on the polarization coupling testing is analyzed, testing method with random polarization state exited has been proposed. Using optimized polarization projection angle, the interference fringe contrast can be improved, and the polarization coupling intensity testing sensitivity can be improved 10dB. A polarization adjusting mechanism is realized based on the transmission light of the analyzer, and the wavelength dependency of the polarization adjusting system is avoided by rotating the Glan prism directly.4. After grasping the time-frequency property of the scanning white light interference data, a group of algorithm are put forward for the detection of polarization coupling point in PMF, including wavelet de-noise, coupling point automatically recognition using time-frequency region analysis, and white light interference envelope extraction using nonlinear regression.5. Based on polarization coupling principle and the instrument has been developed, six applications of testing of PMF ring and polarization passive components, principle axes alignment of PMF, beat length measurement, distributed sensing, and charactering birefringence dispersion of PMF have been realized.
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