Analysis of third-order nonlinearity effects in very high-Q WGM resonator cavity ringdown spectroscopy

International audienceThe time domain coupled-mode theory (CMT) is applied to the analysis of the dynamic of third-order optical nonlinear effects in high-finesse whispering-gallery-mode (WGM) resonators. We show that this model is well adapted to the analysis of cavity-ringdown spectroscopy signal under modal-coupling due to Rayleigh backscattering in linear and nonlinear regimes. The experiments are carried out in silica WGM microspheres. Considering thermal and Kerr effects, CMT simulations are in good agreement, with experimental results for input power up to about 1 mW. For well-known optical materials such as silica, this experimental data analysis method can be used to measure the quality factor, the coupling regime, and the mode volume of high-finesse WGM. Furthermore, this technique could be developed to infer linear and nonlinear properties of high-finesse coated WGM microspheres

Comparison Of Two Methods For Demodulation Of Pulse Signals - Application In Case Of Central Sleep Apnea

In the field of 24/7 human health monitoring, pervasive computing makes possible the continuous analysis of physiological parameters from an ambulatory device with a great acceptability. This paper presents two methods for obtaining cardiac and respiratory rates from a single arterial pressure signal: AM-FM demodulation and Singular Spectrum Analysis (SSA). With the aim to monitor sleep apnea, two simulated central sleep apnea were performed and recorded with Biopac reference system. The results showed a good evaluation of the cardiac rate with Singular Spectrum Analysis and bad results with AM-FM demodulation. For the respiration rate, some other signals were tested with average results for both methods. Further experiments will deal with real sleep apnea cases and algorithm improvements

Modal decomposition technique for multimode fibers

International audienceWe propose a new solution for modal decomposition in multimode fibers, based on a spectral and spatial imaging technique. The appearance of spurious modes in the spectral and spatial processing of the images at the output of the fiber under test when it has more than two modes is demonstrated theoretically. The new method, which allows us to identify spurious modes, is more accurate, simpler, and faster than previously reported methods. For demonstration, measurements in a standard step-index multimode fiber and a small-core microstructured fiber are carried out successfully

Physical and Optical Properties of Poly(3-AlkylThiophene) with a View to the Fabrication of a Highly Nonlinear Waveguide

Publisher: Bentham (ISSN: 1874-088X)International audienceIn order to take advantage of the very high nonlinear susceptibility of conjugated polymer materials, Poly(3-AlkylThiophene)s, P3AT, were synthesized in the laboratory. The physical, thermomechanical and linear optical propertiesof synthesized P3AT have been investigated and the first experimental attempts at creating nonlinear optical waveguides and determining their characteristics are presented. After synthesizing P3AT, the relationships between polymer chain characteristics and mechanical properties are investigated to see if the polymer is suitable for optical waveguide process technology. We also examine the optical attenuation of the synthesized material, a crucial factor in anticipating the relative opacity of the future component. For the first time we present the absorption spectrum of 3-Octylthiophenemolecules in the Near Infra-Red (NIR) region that suggests optical losses for the material are about 0.6 dB.cm-1 at 1550 nm. Next we examined several waveguide structures such as ridge, buried and Strip Loaded WaveGuides (SLWG) based on P3AT material. For the buried waveguides, we have observed the signal transmission and in our opinion the low optical transmission of P3AT ridge and SLWG could be attributed to extrinsic losses (mainly scattering) due to both the remaining insoluble products in the polymer and to the poor adhesion between optical layers

Characterization of Few Mode Fibers by OLCI Technique

International audienceAll LP modes of a few mode fiber are simultaneously characterized using phase-sensitive optical low-coherence interferometry. The differential modal group delay and absolute chromatic dispersion values of each mode are retrieved from a single measurement without spatial mode transformers

All-optical time-domain demultiplexing of 170.8 Gbit/s signal in chalcogenide GeAsSe microstructured fibre

International audienceWe report on four-wave-mixing-based all-optical time-domain demultiplexing of a 170.8 Gb/s signal down to 42.7 Gb/s in a chalcogenide GeAsSe microstructured fiber. The high nonlinearity of the fiber allows error-free and low power penalty operation with only 56 mW of total input average power

A non-destructive method to measure coupling and propagation losses in optical guided structures

International audienceWe propose and demonstrate a nondestructive method for loss measurement in optical guided structures. In the proposed approach, the device under test does not require connectors at its ends, thus making this technique available for both optical fibers and integrated optical waveguides. The loss measurement is feasible over a broad range, from low (0.2 dB/km ) to high (of the order of 1 dB/mm ) loss values. This method is validated through measurements performed on a microstructured holey fiber and on a photonic-crystal waveguide. The obtained results are in good agreement with theoretical calculations and measurements obtained by other approaches

Wavelength conversion in a highly nonlinear chalcogenide microstructured fiber

International audienceWe report on all-optical wavelength conversion of a 56 Gb/s differential quadrature phase shift keying signal and a 42.7 Gb/s on-off keying signal. Wavelength conversion is based on four-wave mixing effect in a 1 m long highly nonlinear GeAsSe chalcogenide fiber. The high nonlinearity of the fiber allows low-power penalty operation with a total average power of less than 60 mW

Versatile Graded-Index Multi-Mode Fiber for High Capacity Single-and Multi-Mode Optical Home Network

International audienceA graded-index multi-mode fiber has been optimized to sustain a single excited mode when coupled with a standard single-mode fiber at 1310/1550nm while offering large effective modal bandwidth at 850nm under VCSEL excitations. Modeling and experimental results are presented

Couplage entre une membrane à cristaux photoniques en matériaux III-V et une fibre micro-lentillée : simulations et mesures

session orale JNOG_2 "Nanophotonique"National audienceDans cet article nous présentons les résultats de simulations et de mesures des profils transverses d'intensité d'un guide réalisé sur une membrane à cristaux photoniques en matériaux III-V ainsi que de couplage entre ce guide et une fibre micro-lentillée. Ces résultats, obtenus dans le cadre du projet européen COPERNICUS, montrent un bon accord entre théorie et expérience