Yang Jiewei, Yang Tianxin, Wang Zhaoying, Jia Dongfang, Ge Chunfeng
Key Laboratory of the Ministry of Education on Optoelectronic Information Technology, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China.
Sensors (Basel). 2020 Jul 9;20(14):3834. doi: 10.3390/s20143834.
Ultrafast linear frequency modulated continuous-wave (FMCW) lasers are a special category of CW lasers. The linear FMCW laser is the light source for many sensing applications, especially for light detection and ranging (LiDAR). However, systems for the generation of high quality linear FMCW light are limited and diverse in terms of technical approaches and mechanisms. Due to a lack of characterization methods for linear FMCW lasers, it is difficult to compare and judge the generation systems in the same category. We propose a novel scheme for measuring the mapping relationship between instantaneous frequency and time of a FMCW laser based on a modified coherent optical spectrum analyzer (COSA) and digital signal processing (DSP) method. Our method has the potential to measure the instantaneous frequency of a FMCW laser at an unlimited sweep rate. In this paper, we demonstrate how to use this new method to precisely measure a FMCW laser at a large fast sweep rate of 5000 THz/s by both simulation and experiments. We find experimentally that the uncertainty of this method is less than 100 kHz and can be improved further if a frequency feedback servo system is introduced to stabilize the local CW laser.
超快线性调频连续波（FMCW）激光器是连续波激光器中的一个特殊类别。线性FMCW激光器是许多传感应用的光源，尤其是用于光探测和测距（LiDAR）。然而，就技术方法和机制而言，用于产生高质量线性FMCW光的系统有限且多样。由于缺乏线性FMCW激光器的表征方法，很难对同一类别的产生系统进行比较和评判。我们提出了一种基于改进的相干光谱分析仪（COSA）和数字信号处理（DSP）方法来测量FMCW激光器瞬时频率与时间映射关系的新方案。我们的方法有潜力以无限扫描速率测量FMCW激光器的瞬时频率。在本文中，我们通过仿真和实验展示了如何使用这种新方法在5000 THz/s的大快速扫描速率下精确测量FMCW激光器。我们通过实验发现该方法的不确定度小于100 kHz，如果引入频率反馈伺服系统来稳定本地连续波激光器，不确定度还可以进一步提高。
