The modeling of the simultaneous propagation of high-power and bidirectional data along the same 10-km-long single-mode fiber is discussed. The intense signal carries the energy needed to supply an instrument in the context of cabled submarine observatories. The considered mathematical description takes into account the fiber’s nonlinear behavior in terms of Raman and Brillouin scattering to describe spectral propagation in the static regime. By testing our model against measurements, its validity is evaluated. Preliminary results are promising and reveal the path to follow for its improvement.
We investigate an acousto-optic tunable filter setup for wavelength division multiplexing telecommunication applications in wideband C (100 nm around 1550 nm). Anisotropic Bragg diffraction of light in TeO2 bulk crystal is first investigated experimentally and theoretically in a quasi-collinear interaction configuration. Based on those characterizations, we propose a double-pass optical beam which allows us to improve the filter performances in terms of crosstalk and selectivity: the full width at half maximum and the sidelobe level are reduced.
Submarine cabled networks are designed to collect valuable data in geophysics, geochemistry, biology, or oceanography. Unfortunately, the development of such a network is expensive and needs complex subsea infrastructures. Once in place, a cabled network cannot be easily relocated. The current cost of cables and their installation are one of the major obstacles to these networks deployment. On the one hand, these cables are necessary to provide power supply and communication data, and on the other hand they drastically reduce the possibilities to extend the cabled observatory network in order to reach a closed area of significant interest. This is why, to address this issue, we propose a quasi-all-optical architecture to easily extend multidisciplinary cabled networks or to create a dedicated submarine hydrophone or seismometer network. This solution consists of using only a single fiber optic to transmit both the energy, required to supply the instrument, and the data, exchanged between the shore station or equivalent. In this paper, we present our proposed architecture, and we discuss its feasibility thanks to experimental results.
A 2×2 switch based on an acousto-optic Bragg cell for telecommunications applications was developed. Two Bragg gratings are superimposed in the same crystal by applying two RF signals simultaneously to the cell. This results in the appearance of spurious optical beams. All the unwanted beam characteristics have been evaluated to optimize the performances of this device. The measurements have been made using an optical heterodyne detection method. The cell is made with a planar phased array transducer with a TeO2 crystal.
Acousto-optic devices play an important role in the field of optical information and communication. For a few years, we have worked on acousto-optic deflection in the Bragg regime at 1.55-µm wavelength, by controlling the rf signal applied to the piezoelectric transducer. Recently, still using the acousto-optic interaction, we have taken an interest in the 2×2 switching function. We present an acousto-optic switch architecture based on phased-array transducers. In the same crystal, we superimpose two diffraction gratings created by two rf signals. Generating a phase shift on a rf signal applied between successive elementary transducers allows us to tilt one grating so as to interconnect inputs to outputs. To predict and study some physical phenomena generated in this switch architecture, we present some characterizations made on a monotransducer cell. We point out the optical cross talk between output paths (influence of the intermodulation products due to the superimposition of two rf signals on the same transducer).
With the intention of developing devices for optical communications, we have worked upon acousto-optic deflection in the Bragg regime, at 1.55 µm wavelength. Recently, still using the acousto-optic interaction, we have taken an interest in the 2×2 switching function. In this paper, we present an acousto-optic switch architecture based on phased array transducers. This switch is made of a single TeO2 crystal, in which we superimpose two diffraction gratings created by two RF signals. First, we talk about the acousto-optic interaction, and make a general presentation of the switch's architecture. Then, we present some previous characterisations of the structure, in terms of diffraction efficiency according to the number of piezoelectric transducers electrically supplied and the RF power applied. We also study the diffracted optical beam profiles.
We describe in this paper the architecture of a multiphase sinewave generator based on Direct Digital Synthesis techniques. This generator is used as the electric command of a 2?2 switch with an acousto-optic cell architecture using planar phased array piezoelectric transducers. This generator is able to adjust precisely the frequency and the phase of the RF signal on each transducer, and so to improve the switch performance.
Acousto-optic devices play an important role in the field of optical information and communication. For a few years, we have worked upon acousto-optic deflection in the Bragg regime, at 1.55 µm wavelength, by controlling the RF signal applied to the piezoelectric transducer. Recently, still using the acousto-optic interaction, we have taken an interest in the 2×2 switching function.
In this paper, we present an acousto-optic switch architecture based on phased array transducers. In the same crystal, we superimpose two diffraction gratings created by two RF signals. Generating a phase shift on an RF signal applied between successive elementary transducers allows us to tilt one grating so as to interconnect inputs to outputs.
In order to predict and to study some physical phenomena generated in this switch architecture, we present some characterizations made upon a mono-transducer cell. We point out the optical cross talk between output paths (influence of the intermodulation products due to the superimposition of two RF signals on the same transducer) and the electrical cross talk influence on optical diffraction efficiency.
We propose a novel synchronous switch for telecommunication networks at a 1.5 μm wavelength. This switch is based on the acousto-optic interaction. In this paper, we discuss about the switch's constraints to be applicable in a network, and present an acousto-optic cell architecture using planar phased array piezoelectric transducers.
In this paper we present a new application of acoustooptic cell used as a fast deflector. First, we have measured the principal performance of the acoustooptic cell like the diffraction efficiency, the number of deflection points, the switching time and the geometry of the diffracted beam. Afterwards we present an application of the optical fast deflector for telecommunication network. It is an optical packets synchronizer device based on the association of acoustooptic cell and fiber delay lines.
A spatial coherence analysis of the light scattering in turbid media, illuminated by a laser source, is presented. Classical degree of coherence modulus measurements require the determination of a fringe pattern visibility. This measurement needs complex algorithms for detecting the fringes minima and maxima on the digitized image. We describe here an easy method to extract the average visibility from the digitized fringe pattern histogram. In the first part, we present the mathematical basis of the method which is obtained from the classical intensity distribution of an interference pattern. This method requires slow spatial variations fringes size compared with the spatial carried frequency. Furthermore, the intensity of the two arms of the interferometer must be equal. If these conditions are assumed, we can easily extract the degree of spatial coherence modulus directly from the histogram of the fringe pattern. The efficiency of the method has been proved using computed interference fringes. In the second part, we apply the histogram analysis on real fringe interference measured in turbid media (seawater). The estimated spatial coherence magnitude is compared with results obtained by classical method. This comparison shows the validity of the histogram method. In conclusion a discussion is made about the advantages and the limits of the proposed method.
To study the influence of sea-perturbations on an optical wavefront in coherent detection through the air-sea interface, we have used two experimental methods based on interferometric techniques. We use Michelson interferometry and Fourier transform to determine wavefronts deformations after double passage through a wavy air-water interface. We consider the statistical aspect by using the averaged Fourier spectra over many independent realizations. Then, a spatial coherence analysis of light scattering in turbid water is presented: the module of the degree of spatial coherence across the beam section is measured by a Mach-Zehnder interferometer.
We describe an experimental method, using Michelson Interferometry and fourier transform, to determine wave fronts deformations after double passage through a wavy air-water interface. We consider the statistical aspect by using the averaged fourier spectra over many independent realizations. The spreading of fourier spatial spectra obtained from interferometric images can be used to determine heterodyne efficiency in airborne hydrographic systems using optical coherent detection.
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