Measurement of beat length of PANDA polarization maintaining fibers by differential group delay method

Abstract

In this paper, the DGD (Differential Group Delay) method for beat length measurement of PANDA polarization maintaining (PM) fibers is theoretically analyzed in detailed. And the analysis indicates, regarding the series of silica optical fibers, the error of beat length at different testing wavelength can be ensured less than 2% based on present fiber designs and germanium-doped concentration level. Presently the PMD400 (Polarization Mode Dispersion) analyzer is applied to measure the beat length of polarization maintaining fibers at Yangtze Optical Fiber and Cable Company. Lots of test results shows the DGD method is very reliable, convenient and nondestructive. In practical, the relative deviation of beat length at different wavelength can be kept under 1.5% below based on a number of experimental data. Therefore, the DGD of a PM fiber can be tested at a definite wavelength, such as 1550nm, and then the beat lengths at other operating wavelength can be got according to the relationship between beat length and operating wavelength.