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在布里渊光时域反射计(BOTDR)的相干检测系统中,为减小偏振失配对布里渊谱测量精度的影响,针对后向布里渊散射光偏振态沿光纤随机变化,而同一记录点在重复采样周期内几乎不变的特点,结合偏振分集和扩展的思想,提出了实现简单而有效的时域偏振分集技术。理论分析表明,不管布里渊散射信号光的偏振态如何随机变化,采用该技术有较稳定的信号光功率与本振光被外差接收,接收信号对偏振态随机变化不敏感。系统实际上可基本不改变原系统体系,只对本振光施以无循环反馈的简单偏振控制。在布里渊时域反射计系统中实验对比了采用与不采用该技术的结果,表明前者的接收信号功率幅度约是后者的四分之一,抑制幅度起伏效果明显。
In the coherence detection system of Brillouin optical time-domain reflectometer (BOTDR), in order to reduce the influence of polarization mismatch on the measurement of Brillouin spectrum, the polarization state of backward Brillouin scattering light changes randomly along the optical fiber, The recording points are almost invariant during the repeated sampling period. Combined with the idea of polarization diversity and expansion, a simple and effective time-domain polarization diversity technique is proposed. The theoretical analysis shows that no matter how the polarization state of Brillouin scattering signal changes randomly, the more stable signal power and local oscillation light are received by heterodyne, and the received signal is not sensitive to the random variation of polarization state. In fact, the system can basically change the original system without adding any simple polarization control to the local oscillator without feedback. In Brillouin time-domain reflectometer system, the experimental results with and without the use of the technology show that the former received signal power amplitude is about a quarter of the latter, the suppression of amplitude fluctuation effect is obvious.