Fast retrieval of atmospheric CO2 concentration based on a near-infrared all-fiber integrated path coherent differential absorption lidar

An all fiber coherent differential absorption lidar (CDIAL) system working in the 1.57 μm wavelength region was developed and the research on fast retrieval of atmospheric CO2 concentration is experimentally demonstrated. Two narrow-linewidth fiber lasers are used and controlled by an optical switch to achieve time division multiplexing. The feasibility of polarization diversity reception (PDR) is analyzed based on randomly oriented elliptically polarized light to improve the polarization matching between the lidar return and local oscillator (LO); moreover, the performance of pulse coherent accumulation is simulated on the grounds of random initial phase correction of laser pulses. Detection experiments show that the relative fluctuations of intermediate frequency (IF) signal could be reduced to 0.41% with PDR; the minimum detection limit of this CDIAL system is better than 4 ppm in less than 1 s in 1 km and it can be used to monitor the short-term changes of atmospheric CO2 concentration. Due to the capability of polarization matching and coherent accumulation, our CDIAL system is promising to improve the temporal resolution of range resolved lidars for atmospheric CO2 detection when there is a more powerful emitter.