Sea floor characterization by means of nonlinear multi-frequency generation

For some years, there has been a growing interest for techniques to achieve seafloor characterization. It is known that the frequency diversity provides essential information to derive the nature of the seafloor: a major challenge is to correlate consistently data obtained in different conditions with several systems. We investigated a new concept based on a transmitter that generates simultaneously several harmonic frequencies by means of the saturation effect. The source is unique in time and space so that the multi-frequency responses are inherently perfectly matched. The receiver is a rectangular multi-element broadband array realized for measurements in the sea environment. Seabed characterization measurements were made in the bay of Brest. First results of sediment backscatter response and seafloor images are presented.