A New Embedded Full Strain Components Sensor

International audienceA new concept of strain (or stress) tensor sensor is presented. Fully embedded in the structure, it measures the full 3D strain tensor while suppressing its own influence, i.e allowing to find the strain (or stress) that would exist without the sensor, thanks to the Eshelby theorem. Furthermore, this theorem proves that the strain field is homogenous in the spherical (or ellipsoidal) body of the sensor, leading to perfect conditions of use for the six Bragg grating glass fibers which measure the strain of the body. After a brief overview of the theory, both mechanical and optical, we will present the results of the test performed using a prototype. This device is a simplified version of the sensor (3 channels) submitted to a hydrostatic pressure in order to assess the precision and the repeatability of the measure

Graded and step index buried optical waveguides fabricated from p-type porous silicon : Processing and measurements

International audienceThe realisation of optical buried waveguides fabricated from porous silicon layers is presented. The refractive index of porous silicon layer varies according to its porosity and its oxidisation process conditions. So either step or graded index waveguides are achieved. These waveguides are formed by a localised anodisation of heavily doped P-type silicon wafers. Measurements at a wavelength of l.ôum yield waveguide losses below 4 dB/cm

Optical characterization of PZT thin films for waveguide applications

International audienceIn order to develop an electro-optic waveguide, Pb(Zr, Ti)O3 ceramic ferroelectric thin films were elaborated by a modified sol-gel process on glass substrate. In the aim to study the optical properties of the PZT films, an accurate refractive index and thickness measurement apparatus was set up, which is called M-lines device. An evaluation of experimental uncertainty and calculation of the precision of the refractive index and thickness were developed on PZT layers. Two different processes of PZT elaboration were made and studied with this apparatus. The reproducibility of one fabrication process was tested and results are presented in this paper

Ultra-wideband GCPW-MS-GCPW driven electrode for low-cost and wide range application electro-optic modulators

International audienceElectro-optic modulators are key components in high bit-rate optical transmissions. Decreasing the manufacturing cost without damage on performances is one of the most challenging issues for such components. We demonstrate that the electro-optic modulators based on polymer are compatible with high bandwidth requirements. Indeed, according to the results obtained by numerical simulation and partly validated by experiments, with the via-free GCPW-MS-GCPW electrodes proposed and analyzed in this article, the (400 MHz–67 GHz) bandwidth is achievable with electro-optic modulators based on suitable polymers. These encouraging results are very useful for low-cost mass production of polymer-based electro-optic modulators for a wide range of applications: digital and analogue high bit-rate transmissions

Coplanar-Microstrip Transitions for Ultra-Wideband Communications

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Mesure de gradients de déformations par fibre optique = Strain gradient measurement with optical fiber

National audienceCet article porte sur l'utilisation de fibre optique à réseau de Bragg pour mesurer des profils de déformations non uniformes. Les réseaux de Bragg permettent facilement de mesurer des déformations uniformes, notre méthode est donc expliquée pour mesurer des gradients de déformations. Cette méthode est ensuite testée sur une éprouvette en résine, et les résultats comparés à une simulation numériques. Des fibres optiques à réseau de Bragg sont ensuite insérés dans des éprouvettes en composites stratifiés afin de caractériser les variations de déformations à travers les plis soumis à des sollicitations de flexion

Superposition of fiber Bragg and LPG gratings for embedded strain measurement

AbstractWhen a fiber Bragg grating strain sensor is embedded inside a structure, the interaction of the sensor with the host material can lead to spurious results if the radial strain is neglected. In this article, we use numerical simulations to show that the axial and radial strains can be simultaneously measured with a single fiber in which a Bragg grating and a long-period grating are superimposed. Moreover, we present an optimal architecture of the sensor