Zhang Yichi, Wang Jianfei, Chen Mo, Wang Mingyang, Liang Yan, Meng Zhou
College of Meteorology and Oceanology, National University of Defense Technology, Changsha 410073, China.
Academy of Artillery and Air Defense, Nanjing 210000, China.
Sensors (Basel). 2020 Oct 30;20(21):6180. doi: 10.3390/s20216180.
The 3 × 3 demodulation algorithm has been widely used in retrieving the phase information in the optical fiber sensing system, while the asymmetry of the 3 × 3 coupler can introduce some distortions. In this situation, the parameters of the 3 × 3 coupler can be calibrated by the ellipse fitting method to remove the distortions. Conducting a frequency modulation on the laser, together with an unbalanced Michelson interferometer, makes the ellipse fitting method implemented, which is more appropriate for all-optical sensing. Unexpectedly, the auxiliary amplitude modulation of the laser induced by the frequency modulation is inevitable, leading to the deterioration of the calibration. In this paper, the influence of the auxiliary amplitude modulation on the calibration of the asymmetric parameters is analyzed theoretically and verified experimentally, on the basis of which a convenient but highly efficient method for acquiring the output of the laser and removing related items from the interferometric signals is put forward. The feasibility and robustness of the proposed solution is tested experimentally, and the results show that the mean square errors of the fittings and the variation coefficients of the calibrated parameter sequences are at the scale of 10-5 and 10-4, respectively, indicating that the method performs very well.
3×3解调算法在光纤传感系统中获取相位信息方面已得到广泛应用，然而3×3耦合器的不对称性会引入一些失真。在这种情况下，可通过椭圆拟合方法对3×3耦合器的参数进行校准以消除失真。对激光器进行频率调制，并结合不平衡迈克尔逊干涉仪，可实现椭圆拟合方法，该方法更适用于全光传感。出乎意料的是，频率调制引起的激光器辅助幅度调制不可避免，导致校准变差。本文从理论上分析了辅助幅度调制对非对称参数校准的影响，并进行了实验验证，在此基础上提出了一种简便但高效的获取激光器输出并从干涉信号中去除相关项的方法。对所提解决方案的可行性和稳健性进行了实验测试，结果表明拟合的均方误差和校准参数序列的变异系数分别在10⁻⁵和10⁻⁴量级，表明该方法性能良好。
