All-fiber 1.5 μm CW coherent laser anemometer for in-flight measurements

In order to optimize their flight conditions, airborne platforms need to know precisely their true airspeed. In helicopters, measuring low air speeds is a severe issue because of the rotor flow. Optical air data sensors are therefore a good alternative to classical pneumatic probes. ONERA is involved for many years in simulation and design of coherent lidar and focuses its last research on eye-safe solid state lidars. This paper describes the study of performance of a reliable compact airborne system based on a 1.5 mum Erbium fiber laser and architecture. The average heterodyne current power is examined for the case of negligible turbulence and truncation effect. The spatial resolution of the measurement is deduced and its behavior versus transmitter beam parameters discussed.