Patrice Mégret

Learn More
Nowadays, smart composite materials embed miniaturized sensors for structural health monitoring (SHM) in order to mitigate the risk of failure due to an overload or to unwanted inhomogeneity resulting from the fabrication process. Optical fiber sensors, and more particularly fiber Bragg grating (FBG) sensors, outperform traditional sensor technologies, as(More)
Vertical-cavity surface-emitting lasers subjected to weak polarization-insensitive optical feedback are studied experimentally and theoretically. We find that the feedback induces random anticorrelated hopping between the two orthogonal linearly polarized modes. This polarization mode hopping is accompanied by rapid anticorrelated oscillations in the(More)
Using hydrogen as fuel presents a potential risk of explosion and requires low cost and efficient leak sensors. We present here a hybrid sensor configuration consisting of a long period fiber grating (LPFG) and a superimposed uniform fiber Bragg grating (FBG). Both gratings are covered with a sensitive layer made of WO(3) doped with Pt on which H(2)(More)
Optical fiber sensors (OFS) are developed to replace conventional electro-mechanical sensing systems, which are well established, have proven their reliability and can be manufactured at low cost. Advantages of OFS are resistance to electromagnetic interference, intrinsic safety, mechanical simplicity and small size, the possibly of high sensitivity and(More)
We propose a technique for measuring both pulse width and amplitude jitter noises of high-repetition-rate optical pulse trains and the cross correlation between these noises as well. The technique is based on time-domain amplitude demodulation of three harmonic components of the detected pulse train. We applied this technique to characterize noises of a(More)
Alain Delchambre Université libre de Bruxelles CP 165/41, 50 av. F.D. Roosevelt B-1050 Brussel, Belgium Abstract. In-core temperature measurement is a critical issue for the safe operation of nuclear reactors. Classical thermocouples require shielded connections and are known to drift under high neutron fluence. As an alternative, we propose to take(More)
A. I. Gusarov is with the Faculté Polytechnique de Mons and also with the SCK·CEN Belgian Nuclear Research Centre, Mol, Belgium. D. S. Starodubov is with D-STAR Technologies, Inc., USA. F. Berghmans is with the SCK·CEN Belgian Nuclear Research Centre, Mol, and also with the Vrije Universiteit Brussel, Belgium. O. Deparis, Y. Defosse, P. Mégret, and(More)
We quantify the refractive index changes (RIC) in single-mode ytterbium-doped optical fibers induced by optical pulses at 980 nm and, for the first time, report details of the effect dynamics. The RIC dynamics is shown to follow that of the population of the excited/unexcited ion states with a factor proportional to their polarizability difference (PD). The(More)
Fiber optical current sensor (FOCS) is a technique considered to be compatible with the ITER nuclear environment. FOCS principle is based on the magneto-optic Faraday effect that produces non-reciprocal circular birefringence when a magnetic field is applied in the propagation direction of the light beam. The magnetic field or the electrical current is(More)
The high order cladding modes of standard single mode optical fiber appear in quasi-degenerate pairs corresponding to mostly radially or mostly azimuthally polarized light. In this work, we demonstrate that, in the presence of a high-refractive-index coating surrounding the fiber outer surface, the wavelength spacing between the orthogonally polarized(More)