研究了基于3×3耦合器的非平衡迈克耳孙干涉仪的相位特性。由光纤耦合器的散射矩阵理论,推导出了当3×3耦合器分光比不均匀时,干涉仪三路输出信号相位差的表达式。根据实际使用的3×3耦合器各通道的插入损耗,经计算与修正得到其散射矩阵,并求出干涉仪三路输出信号的相位差分别为120.21°、120.77°和119.02°,与理想值120°的偏差在1°以内。实验测得的干涉仪三路输出信号的相位差随时间随机变化,经分析是由光偏振态随机变化引起的。相位差与理想值120°的偏离均在1°以内,符合理论分析得到的结论。

The phase characteristics of an unbalanced Michelson interferometer based on a 3×3 coupler was investigated. Using the scattering matrix theory of fiber couplers, the phase differences between each two of the three outputs of the interferometer were deduced when an unideal 3×3 coupler was used. The scattering matrix of a commercial 3×3 fiber coupler was obtained from the insert loss of each channel after calculation and modification. The phase differences of the three outputs of the interferometer are calculated to be 120.21°, 120.77° and 119.02°, with deviation less than 1° from the ideal 120°. An experiment was carried out to measure the three outputs of the interferometer. Small fluctuation of the phase differences is observed, which is due to the random change of polarization state. The maximum of the deviations from the ideal 120° is within 1°, and the experimental results are in accordance with the theoretical expectations.