Doppler Lidar Systems

What is “Doppler Lidar ”? – Technologies

Lidar system

Mitsubishi Electric's Doppler Lidar applies the Coherent Doppler Lidar method. A Coherent Doppler Lidar transmits high-quality, single-wavelength laser pulses into the air and receives the light backscattered from aerosols. The frequency of the received light is shifted due to the movement of aerosols (Doppler effect). This Doppler shift, which corresponds to the velocities of the aerosols, is extracted using heterodyne detection. Applying high-speed signal-processing technology, our Lidar systems accurately calculate Doppler velocity and the resultant wind speed (i.e., movement of air).

Laser technology

Mitsubishi Electric’s Doppler Lidar adopts an all-fiber system to realize its compact, lightweight size and highly reliable data.

Also, we have developed and manufactured a planar waveguide type amplifier called a Wave Guide Amplifier (WGA) which increased the wind speed measurable range of the lidar significantly.

The conventional Q-Switch Laser Oscillator had a problem in its reliability and frequency stability. By implementing a direct amplification method using the WGA, Mitsubishi Electric was able to realize frequency stability and environmental resistancy.

Wave Guide Amplifier (WGA)

Optical-fiber Doppler Lidar

All of the optical elements are connected using optical fiber, making the system configuration compact, flexible, and unaffected by environmental factors such as temperature and vibration.

Output laser

Fiber laser
(Fiber amplifier)

Output peak
power
Low
(1~20W)
Pulse repetition
frequency

High
(10~100kHz)

High average output power available

Conventional Lidar

The output from the laser is free-space propagated between the output laser and the optical transmitting/receiving (Tx/Rx) system, so a large configuration is required. This makes the system vulnerable to the operating environment such as temperature and vibration.

Output laser Diode pumped
solid state laser
Output peak
power
High
(10~100 kW)
Pulse repetition
frequency
Low
(10~100 Hz)

Maximum output is determined by component breakdown limit

Signal-processing technology

Mitsubishi Electric Doppler Lidar systems use high-speed digital signal-processing technology that digitizes the received signals using A/D conversion, conducts frequency analysis at high speed, and outputs the processed data in real time.

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