Improvement of LIDAR system by modulation of an optical pulse laser for underwater detection
Lagaye, J.-P.; Vinay, L.; Richou, J. (1997). Improvement of LIDAR system by modulation of an optical pulse laser for underwater detection, in: Sensors, sensor systems, and sensor data processing: June 16-17 1997, Munich, FRG. Proceedings of SPIE, the International Society for Optical Engineering, 3100: pp. 417-422. https://dx.doi.org/10.1117/12.287766
In: (1997). Sensors, sensor systems, and sensor data processing: June 16-17 1997, Munich, FRG. Proceedings of SPIE, the International Society for Optical Engineering, 3100. SPIE: [s.l.]. ISBN 978-0819425201. 424 pp., more
In: Proceedings of SPIE, the International Society for Optical Engineering. SPIE: Bellingham, WA. ISSN 0277-786X; e-ISSN 1996-756X, more
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Document type: Conference paper
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- Lagaye, J.-P.
- Vinay, L.
- Richou, J.
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| Abstract |
In a conventional bistatic LIDAR system, a laser pulse is generated and is reflected by the target. The round trip time determines the position of this target. In a greatly scattered medium, like water, the returned target signal is hidden by the random backscatter due to the existence of the suspended particules within the ocean mass. The improvement of the target detection sensitivity is possible in this backscatter clutter by modulating an optical pulse laser. We propose a theoretical study of the behavior of a modulated pulse in the underwater medium. We show that the randomly distributed backscatter does not maintain coherency of the modulation envelope whereas the target signal keeps this information. Due to this, the detection of the modulation envelope tends to suppress the incoherent backscatter clutter thereby improving the target contrast. We present a bistatic scheme detection in underwater medium, simulate it and compare results with a laboratory experiment. Simulation of the laser pulse propagation takes into account the single scattering approximation. Numerical integrals are calculated with an original technical based on the division into cubes of the definition domain. Detection of the modulated envelope is based on a fast frequency filter. The optical source used in the experiment is a 1500 nm laser diode controlled by a modulated current (500 Mhz). The ocean mass is simulated with a plastic fiber. A short pulse (10 ns) is transmitted into fiber. The returning pulse is collected by photodiode and analyzed with signal processing method. Experimental results show the efficiency of the modulated signal by a gain of the SNR ratio. |
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