Original waveforms and optimized signal processing are proposed for frequency-modulated continuous-wave lidar for range finding, velocimetry, and laser anemometry. For range finding, the aim of this signal processing is to extend lidar range and reduce ambiguities. Moreover, the effect of moderate atmospheric turbulence on lidar efficiency is analyzed for infinite and finite targets, taking into account wind-induced bistatism. For laser anemometry, the aim is to measure air speed at the shortest distance farther than the rotor-induced turbulent volume around the helicopter and to avoid parasitic echoes coming from clouds or hard targets in the vicinity of a helicopter.

Frequency-modulated continuous-wave lidar is evaluated for range finding, velocimetry, and laser anemometry. An original signal processing and waveform calibration for range finding leads to a reduction of computational effort while preserving capability for long-range measurement. Multiple target distance measurement is also demonstrated. For laser anemometry, the aim is to avoid parasitic echoes in the vicinity of a helicopter and to measure the air speed at the shortest distance farther than the rotor-induced turbulent volume around the helicopter. Flight tests of this functionality and vortex ring state warning are demonstrated.

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In this paper, we present the development of a laser source for a LIDAR application. This sensor is proposed as a standby instrument to provide a way to measure some aircraft air data such as the air speed. Although such systems already exist, none of them are based on an optical measurement. Thus, the use of a LIDAR would provide a backup channel with different failure modes than existing systems. Our LIDAR system allows determining the air speed through Doppler measurement at a wavelength of 1.55 µm on aerosol particles present around the aircraft. The core of this device is a glass integrated optics continuous DFB laser. Its performances in term of single-frequency, stability, noise and linewidth are assessed in order to ensure the correct operation of the LIDAR system.

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