Chen Zhen, Hefferman Gerald, Wei Tao
Opt Lett. 2017 Mar 1;42(5):1007-1010. doi: 10.1364/OL.42.001007.
This Letter reports a sweep velocity-locked laser pulse generator controlled using a digital phase-locked loop (DPLL) circuit. This design is used for the interrogation of sub-terahertz-range fiber structures for sensing applications that require real-time data collection with millimeter-level spatial resolution. A distributed feedback laser was employed to generate chirped laser pulses via injection current modulation. A DPLL circuit was developed to lock the optical frequency sweep velocity. A high-quality linearly chirped laser pulse with a frequency excursion of 117.69 GHz at an optical communication band was demonstrated. The system was further adopted to interrogate a continuously distributed sub-terahertz-range fiber structure (sub-THz-fs) for sensing applications. A strain test was conducted in which the sub-THz-fs showed a linear response to longitudinal strain change with predicted sensitivity. Additionally, temperature testing was conducted in which a heat source was used to generate a temperature distribution along the fiber structure to demonstrate its distributed sensing capability. A Gaussian temperature profile was measured using the described system and tracked in real time, as the heat source was moved.
本信函报道了一种使用数字锁相环（DPLL）电路控制的扫频速度锁定激光脉冲发生器。该设计用于对亚太赫兹范围的光纤结构进行探测，以用于需要以毫米级空间分辨率进行实时数据采集的传感应用。采用分布反馈激光器通过注入电流调制来产生啁啾激光脉冲。开发了一种DPLL电路来锁定光频率扫频速度。展示了在光通信波段具有117.69GHz频率偏移的高质量线性啁啾激光脉冲。该系统进一步用于探测连续分布的亚太赫兹范围光纤结构（sub-THz-fs）以用于传感应用。进行了应变测试，其中sub-THz-fs对纵向应变变化呈现出具有预测灵敏度的线性响应。此外，进行了温度测试，其中使用热源沿光纤结构生成温度分布，以展示其分布式传感能力。当热源移动时，使用所述系统测量并实时跟踪高斯温度分布。
