The optical fiber deployed in the metropolitan infrastructure carrying high-speed WDM traffic data is used also for network surveillance, identifying and localizing the onset of vibrations and dynamic stress events, potentially dangerous for the integrity of the fiber telecom asset. A coherent approach is adopted in a counter-propagating interferometer to develop a sensing system exploiting the ring layout of the metro network. With respect to usual dual Mach-Zehnder interferometric sensors, where typically the reference arm is kept isolated, in our arrangement we use as reference arm a fiber inside the same deployed cable, minimizing the impact of the city strong environmental noise. Preliminary assessments of the proposed sensing solution have been experimented in a metro ring of 32-km standard single-mode fiber deployed in the city of Turin, Italy, devoted to telecom applications. The sensor is demonstrated to operate preserving the coexistence with the high-speed WDM telecom traffic. With respect to complex and expensive sensing solutions based on pulsed phase-OTDR techniques, in the present case continuous-wave counter-propagating optical signals are exploited and the spatial resolution in dynamic event localization depends only on the receiver sampling rate: in our implementation, by adopting off-the shelf low-cost commercial 20 MS/s sampling boards, 10-meter spatial resolution is experimentally achieved. The proposed sensing solution provides significant added value to the deployed metro fiber infrastructure and the same interferometric approach based on the counter-propagating layout can be easily exploited in metro networks even in case of presence of optical nodes equipped with reconfigurable optical add-drop multiplexers useful for WDM traffic routing.

中文翻译：

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已部署城域光纤基础设施的振动传感


部署在承载高速 WDM 流量数据的城市基础设施中的光纤还用于网络监控、识别和定位振动和动态应力事件的发生，这些事件对光纤电信资产的完整性存在潜在危险。在反向传播干涉仪中采用相干方法来开发利用地铁网络环形布局的传感系统。相对于通常的双马赫-曾德尔干涉传感器，参考臂通常保持隔离，在我们的布置中，我们使用同一部署电缆内的光纤作为参考臂，最大限度地减少城市强烈环境噪声的影响。对所提出的传感解决方案的初步评估已在意大利都灵市部署的 32 公里标准单模光纤地铁环中进行了实验，该地铁环专门用于电信应用。该传感器被证明可以在保持与高速 WDM 电信流量共存的情况下运行。对于基于脉冲相位 OTDR 技术的复杂且昂贵的传感解决方案，在目前的情况下，利用连续波反向传播光信号，动态事件定位中的空间分辨率仅取决于接收器采样率：在我们的实现中，通过采用现成的低成本商用20 MS/s采样板，实验性地实现了10米的空间分辨率。所提出的传感解决方案为已部署的城域光纤基础设施提供了显着的附加值，并且即使在存在配备有可重新配置的光分插复用器的光节点的情况下，也可以在城域网络中轻松利用基于反向传播布局的相同干涉测量方法用于 WDM 流量路由。