Research On Birefringence Dispersion In Polarization Maintaining Fiber With Distributed Polarization Coupling Analyzer

In the measurement of polarization coupling using white light interferometry, the birefringence in fiber is usually considered to be wavelength-independent, and the difference between two orthogonal eigenmodes of polarization maintaining fibers (PMFs) is invariable. In practical measurement, however, the birefringence in PMFs is relative with optical wavelength, the chromatic dispersion coefficient are different in two orthogonal axes. Therefore, birefringence dispersion exists in PMFs. The resolution and measurement range in polarization coupling analyzer is limited obviously due to birefringence dispersion.Based on the distributed polarization coupling analyzer (DPCA) developed in our laboratory, the influence of birefringence dispersion on polarization coupling measurement such as the broadening of interferogram and the decreasing of contrast is analyzed with white-light interference theory. Two schemes for improving resolution and measurement range of DPCA is proposed in this dissertation. In the experiment, the birefringence dispersion theory is testified, and a birefringence dispersion coefficient of 0 .0164ps (k m?nm) of the interested fiber is obtained.Major achievements of this dissertation:1. The coupling point interferogram in Michelson interferometer with unbalanced dispersion arm is analyzed based on white-light interference theory.2. The model of polarization coupling measurement with birefringence dispersion is established, and the coupling point interferogram expression is deduced with this model. The factors that may influence envelop width and interferometric contrast are analyzed. Meanwhile, the expressions of resolution and measurement range are provided when birefringence dispersion is considered.3. Two methods for improving the resolution and measurement range in DPCA are proposed. One is using an optical filter reformative structure in the measurement of polarization coupling and the other is to apply a dispersion compensation structure in one arm of Michelson interferometer.4. The optical filter reformative structure is established, and its improving effect for DPCA is analyzed. A drive circuit of optical switch is also designed in this structure.5. The dispersion compensation structure in one arm of Michelson interferometer is analyzed theoretically, and its feasibility is proved. The interferogram expression equation is deduced, and the use of invariable dispersion media to compensate birefringence dispersion is discussed.6. Experiments are carried out to test the influence of birefringence dispersion on the measurement of polarization coupling, and a good agreement between experimental results and theoretical analysis is achieved. The birefringence dispersion coefficient of the interested fiber is calculated as 0 .0164ps (k m(?)nm).