Yaman Fatih, Nakamura Kohei, Mateo Eduardo, Fujisawa Shinsuke, Batshon Hussam G, Inoue Takanori, Inada Yoshihisa, Wang Ting
Opt Express. 2021 May 24;29(11):17628-17668. doi: 10.1364/OE.426557.
Guided acoustic Brillouin (GAWBS) noise is measured using a novel, homodyne measurement technique for four commonly used fibers in long-distance optical transmission systems. The measurements are made with single spans and then shown to be consistent with separate multi-span long-distance measurements. The inverse dependence of the GAWBS noise on the fiber effective area is confirmed by comparing different fibers with the effective area varying between 80 µm and 150 µm. The line broadening effect of the coating is observed, and the correlation between the width of the GAWBS peaks to the acoustic mode profile is confirmed. An extensive model of the GAWBS noise in long-distance fibers is presented, including corrections to some commonly repeated mistakes in previous reports. It is established through the model and verified with the measurements that the depolarized scattering caused by TR modes contributes twice as much to the optical noise in the orthogonal polarization to the original source, as it does to the noise in parallel polarization. Using this relationship, the polarized and depolarized contributions to the measured GAWBS noise is separated for the first time. As a result, a direct comparison between the theory and the measured GAWBS noise spectrum is shown for the first time with excellent agreement. It is confirmed that the total GAWBS noise can be calculated from fiber parameters under certain assumptions. It is predicted that the level of depolarized GAWBS noise created by the fiber may depend on the polarization diffusion length, and consequently, possible ways to reduce GAWBS noise are proposed. Using the developed theory, dependence of GAWBS noise on the location of the core is calculated to show that multi-core fibers would have a similar level of GAWBS noise no matter where their cores are positioned.
采用一种新颖的零差测量技术，对长距离光传输系统中常用的四种光纤测量了受激布里渊散射（GAWBS）噪声。测量是在单跨距情况下进行的，然后证明其与单独的多跨距长距离测量结果一致。通过比较有效面积在80μm至150μm之间变化的不同光纤，证实了GAWBS噪声与光纤有效面积的反比关系。观察到了涂层的线宽展宽效应，并证实了GAWBS峰宽度与声学模式轮廓之间的相关性。提出了长距离光纤中GAWBS噪声的广泛模型，包括对先前报告中一些常见错误的修正。通过该模型确定并经测量验证，由TR模式引起的去极化散射对与原始光源正交极化的光噪声的贡献是对平行极化噪声贡献的两倍。利用这种关系，首次分离了测量的GAWBS噪声中的极化和去极化贡献。结果，首次展示了理论与测量的GAWBS噪声谱之间的直接比较，二者吻合良好。证实了在某些假设下，总GAWBS噪声可以根据光纤参数计算得出。预计光纤产生的去极化GAWBS噪声水平可能取决于极化扩散长度，因此，提出了降低GAWBS噪声的可能方法。利用所发展的理论，计算了GAWBS噪声对纤芯位置的依赖性，结果表明，无论纤芯位于何处，多芯光纤的GAWBS噪声水平都相似。
