White Paper: Test & Measurement

Single Frequency Fiber Lasers for Doppler LiDAR

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RADAR (RAdio Detection And Ranging) is the process of utilizing electromagnetic waves to determine the location and velocity of distant objects by analyzing changes to the reflected signal. Radar’s potential for military and aerospace applications was recognized in 1934, prompting most of the military powers of the time to begin investing in developing the technology immediately.

As the technology advanced, it quickly became apparent that the higher the frequency (bandwidth) of the RADAR signal, the more information the signal could carry, and therefore result in finer resolution. It is for this reason that engineers started developing laser-based radar systems in the 1960s almost immediately after the invention of the laser in 1960. Over the past 50 years since its initial demonstration, laser RADAR has matured into its own field referred to as both LADAR (LAser Detection And Ranging) or LiDAR (Light Detection And Ranging), depending upon the community.

While there is a wide range of commercial and military applications that have been developed using LiDAR, this white paper focuses on the use of single frequency fiber lasers for an application known as Doppler LiDAR.

Doppler LIDAR takes advantage of the fact that when electromagnetic radiation interacts with a moving object, it experiences a frequency shift that is directly correlated to the velocity of the object. The frequency shift can be used to measure the velocity of solid objects like airplanes, automobiles, or baseballs but it is also widely used to track winds and aerosols.

One of the most common uses of Doppler LiDAR is determining wind speed and direction in wind farms, so the blade angle can be adjusted to optimize the efficiency without overloading the turbine. Another typical example is for aviation safety where abrupt changes in wind speed can be detrimental to air traffic, particularly in crowded airports.

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