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Proceedings Paper

Improvement of LIDAR system by modulation of an optical pulse laser for underwater detection
Author(s): Jean-Pierre Lagaye; L. Vinay; Jacques Richou
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Paper 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.

Paper Details

Date Published: 25 September 1997
PDF: 6 pages
Proc. SPIE 3100, Sensors, Sensor Systems, and Sensor Data Processing, (25 September 1997); doi: 10.1117/12.287766
Show Author Affiliations
Jean-Pierre Lagaye, Univ. de Toulon et du Var (France)
L. Vinay, Univ. de Toulon et du Var (France)
Jacques Richou, Univ. de Toulon et du Var (France)


Published in SPIE Proceedings Vol. 3100:
Sensors, Sensor Systems, and Sensor Data Processing
Otmar Loffeld, Editor(s)

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