Monolithic Integrated Linear Frequency Modulated Dual-Wavelength DFB Laser Chip with High Linearity and Its Application in Long Distance Ranging

The ranging distance and precision of the coherent frequency modulated continuous wave (FMCW) lidar systems are mainly limited by the modulation linearity and the intrinsic line width of the laser sources. To this issue, we design and experimentally demonstrate a monolithic integrated linear frequency modulated (LFM) dual-wavelength (DW) DFB laser with high frequency sweep linearity and without a complicated predistortion compensation system. Our results show that the nonlinearity of the LFM beat signal from the DW-DFB laser chip can reach 0.0146%. Furthermore, using the LFM DW-DFB laser, we implement an accurate measurement of a single mode fiber (SMF) with a length of 12.6 km, which is hundreds of times the intrinsic coherent length of the DW-DFB laser. Due to the high linearity of the LFM DW-DFB laser, the measurement error does not deteriorate significantly when the target distance increases from 0.43 to 24.24 m.