The temporal frequency response of water supplemented with scattering particles was deduced from the measurement of the optical backscattering of a short (100 ps) blue-green (532 nm) optical pulse given by a frequency-doubled Nd:YAG laser. Indeed, this backscattering measurement gave the water impulse response from which the transfer function was computed by taking the power spectrum. This backscattering frequency response had a low-pass filter-like response which enabled us to estimate the medium cut-off frequency. As the backscattered signal shape depends on the value of the water attenuation coefficient, the ocean water cut-off frequency varies with the amount of scattering particles its contains. The aim was to define the variations of the cut-off frequency as a function of the attenuation coefficient.

We have experimentally assessed the efficiency of a new underwater-target detection scheme, called modulated lidar. The technique used is based on a remarkable physical property of the propagating medium; sea-water has a low-pass transfer function in backscattering configuration. As the target return is less frequency-dependent, the use of a radio frequency modulated laser source along with a narrow band filtering at the detection drastically reduces the backscattering clutter, but does not affect the target return; the modulation frequency of the source is substantially above the cut-off frequency of the propagating medium. This technique allowed us to greatly improve underwater-target contrast. We associated with this frequency detection a temporal localization of the underwater target by using a pulse-modulated laser source.

Reflection polarization transformations by a given sample depends both on the composition and surface state and on the illumination angle. In the present work, the evolution of polarization transformation given by dielectric samples and metallic surfaces has been studied. The initial metallic surface was polished up to m and then progressively debased. The polarimetric characteristics are described by using the Mueller matrix, which provides the depolarization index, namely the mean depolarization power, and the degree of polarization for all the pure incident states of polarization. The polarization of each sample is measured for various angles of incidence. The noise is reduced by a statistical method to optimize the matrix elements. The results obtained are first presented in a global matrix form and then the depolarization phenomenon is analysed. In the last step the studied samples are characterized and classified.

Although the method based on the Mueller matrix for the experimental determination of optical-device polarization behaviour is a powerful tool, it has rarely been applied to optical fibre. This paper introduces an experimental methodology for measuring the Mueller matrices of monomode fibre under uniform strains. Using a theoretical model derived from coupled-mode equations, we were able to first estimate the physical parameters of the fibre, then to use them to both test the model validity and assess their influence on the polarimetric behaviour of the fibre.

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The Mueller matrix method is powerful for the experimental determination of optical devices polarization behaviors. In the particular case of optical fiber, this method has rarely been used. An experimental methodology for measuring Mueller matrices of monomode fiber under uniform strains is presented. On the base of a theoretical model derived from coupled-mode equations, the physical parameters of the fiber can be estimated. These estimate parameters can then be used to test the validity of this model and to evaluate their influence on the polarimetric behavior of the fiber.

We show the effect of multiple scattering on the shape of the pulse returned by a modulated lidar for bathymetry studies. Multiple scattering lengthens the tracks of individual photons, and consequently broadens pulse shape destroying the modulation. However, the reduction of the detector field of view allowed us to sharpen the pulses and to restore the modulated signal.