Laser Doppler radar is an exciting radar that uses a Doppler system to obtain target motion information. Because of the high coherence, monochromaticity, and directivity of laser, heterodyne detection is possible. The lidar, which receives the frequency shift information of laser Doppler and obtains the radial velocity component using the optical heterodyne detection technology, is called the coherent Doppler lidar.

Principle of velocity measurement

Working mode
1. Direct detection1. Direct detection
2. Heterodyne detection
   In heterodyne detection, the Doppler shift FD of the scattered light is obtained directly by mixing the local and backscattered light.
   The long-distance operation of CDL usually adopts pulse mode, and the detection mode adopts self-phase heterodyne coherent detection.
   The long-distance operation of CDL usually adopts pulse mode, and the detection mode adopts self phase heterodyne coherent detection

                                           continuity                                                                                                         pulse

Working principle
     The laser Doppler radar principle is to measure the radial velocity V of the target according to the Doppler frequency shift FD caused by the target velocity movement, which is based on the coherence of the laser and the square-law characteristics of the detector. The coherent detection method is used in the coherent optical Doppler radar.

     Principle of coherent detection

application:

1. It is used for airborne or airport, real-time monitoring of "clear sky" low wind shear, and providing safety alarm for aircraft takeoff and landing

2. It is used in the space launch site to improve the safety factor of rocket and space shuttle launch

3. For numerical weather prediction, airborne lidar can continuously detect the atmospheric structure and small and medium-sized phenomena. After weather analysis, it can give accurate prediction of local weather situation. Space-based Doppler radar can make overall prediction of large-scale weather situation, which is helpful for climate research.

The products of fiber amplifier and balance detector that can be used in Doppler lidar system are as follows

KG-EDFA

KG-APD