光纤干涉仪的消光比在很大程度上决定了干涉型光纤传感系统的灵敏度从而决定了干涉仪的应用范围和前景。简要介绍了目前超长距离光纤干涉传感系统的发展现状，并在理论上分析了光纤传感系统中的偏振态对消光比的影响以及能够影响光波偏振态的各种因素。将基于光弹效应的挤压型偏振控制器应用于该系统的消光比调谐，给予光纤干涉臂径向应力，动态调谐系统光波偏振态，实现了长距离光纤传感系统的消光比在一点上的调谐。提出了长距离光纤传感系统灵敏度的新调谐方法，消光比动态调谐范围为0.21～11.03 dB。

Optical interferometer extinction ratio determines the sensitivity of interferometric fiber optic sensor system to a large extent and further determines the range of applications and prospects of interferometer. The outline of the current ultra-long distance optical fiber interferometric sensing system development status, the theoretical analysis of the impact of polarization on the optical fiber sensing system, and a variety of factors which can affect the polarization are given. The squeeze-type polarization controller based on photoelastic effect is used to tune the extinction ratio of the system by providing radial stress to fiber interferometer arm, to tune system polarization state dynamically, which makes it possible to molerate the extinction ratio of a long-distance optical fiber sensing system at one point. A novel tuning method to tune the sensitivity of long-distance fiber optic sensing system is proposed, and the range of dynamic extinction ratio of tuning is 0.21～11.03 dB.