Basic Principle of Magneto-Optical Switches and Their Application in Wind Lidar

Magneto-optical switches utilize the Faraday magneto-optical effect. By altering the applied magnetic field, the effect of a magneto-optical crystal on the polarization plane of incident polarized light is changed, thus achieving optical path switching. Compared to traditional mechanical optical switches, magneto-optical switches offer significant advantages: switching speeds reach the μs level, and they feature low polarization sensitivity, no moving parts, low insertion loss, fast response, high integration, low crosstalk, and small size. They can meet requirements such as strong anti-interference capability, low driving voltage, high stability, simple circuit design, high reliability, and long-term continuous operation.

Wind lidar operates in harsh outdoor environments, often unattended, requiring long-term continuous measurements. In addition to switching speed, extremely high reliability and stability are essential. Magneto-optical switches, with their unique advantages, meet the needs of wind-measuring radar. Specific applications are as follows: The laser emitted by the laser source system is coupled to an optical antenna via optical fiber. The radar is equipped with four beam-emitting lenses, angled horizontally at 30° and vertically at 25°. The four laser beams switch at a frequency of 50Hz.

The light is focused by a lens in the optical antenna to a fixed distance, where the energy is most concentrated. It then scatters with the aerosol at that point. The scattered light is coupled back into the optical fiber via the lens, where it is mixed with the local oscillator light generated by the laser source system in the coupler. The photoelectric conversion module then converts the optical signal into an electrical signal and amplifies it. The data acquisition system collects the electrical signal and performs spectrum processing. Finally, the data processing system calculates the wind speed information for that single channel based on the spectrum.