A 10-km Polarization Maintaining Fiber Distributed Polarization Coupling Measurement Method With Dispersion Compensation Function Based on White Light Interferometer

Polarization-maintaining fibers (PMFs) with a length of over 10 km are widely employed in fiber gyros and other fields. Distributed polarization coupling (DPC) characterizes the polarization conservation ability of PMFs. Measuring the DPC of 10-km PMF is difficult due to the limitation of scanning range in white light interferometry (WLI). Moreover, the influence of dispersion on the interferograms becomes increasingly serious with the increase in fiber length. We proposed a method to measure the DPC for 10-km PMFs based on all-fiber WLI. In all-fiber WLI, a 3-dB coupler and compensation fibers of different lengths are inserted into the stable arm and moving arm, respectively. When the 3-dB coupler is closed to form the ring cavity, the measurement system works in calibration mode; otherwise, it works in measurement mode. In calibration mode, the interferograms contain multiple interference peaks for periodic delay of the ring cavity. According to the peaks, the data fragments from measurement modes are spliced together, consequently producing the measurement results for 10-km PMF. Then, a dispersion compensation method is proposed based on frequency-domain transformation to improve the measurement accuracy of DPC and space resolution. The experimental results demonstrate that the coupling intensity and space resolution are restored. The achievements in this article are beneficial to optical fiber sensing and optical fiber communication.