Much effort has been focused on the development of frequency modulation continuous waves (FMCW) light sources which are used in Light Detection And Ranging (LiDAR) systems. However there has not appeared a method or instrument which can measure the instantaneous frequency and dynamic linewidth of the FMCW light source over the whole frequency sweep range of about several hundreds of GHz with an accuracy down to kHz. In this paper a new method is proposed for measuring the dynamic frequency properties of FMCW light sources in real-time and several experimental setups are built for the feasibility study.
The frequency modulation continuous wave (FMCW) light detection and ranging (LIDAR) has drawn enormous attention and intense effort. In this paper a nonlinear tuning technique for a DFB laser which is driven by a home-made LD driver is proposed and developed experimentally for generation of linearly chirped light which may be applied in FMCW LIDAR systems. A frequency predistortion procedure based on nonlinear tuning technique can be applied to the LD driver which could be controlled by a field-programmable gate array (FPGA) module. And the frequency predistortion procedure can be used iteratively until the desired linearity of the chirped optical waves is achieved before the PLL is introduced in. This technique can be seen as an effective way to increase the acquisition bandwidth of the PLL significantly so that the trade-off between large acquisition frequency and narrow bandwidth of the PLL is no longer a problem.