Three-hole microstructured optical fiber for efficient Fiber Bragg Grating refractometer

International audienceWe present a photosensitive three-hole microstructured optical fiber specifically designed to improve the refractive index sensitivity of a standard Fiber Bragg Grating (FBG) sensor photowritten in the suspended Ge-doped silica core. We describe the specific photowriting procedure used to realize gratings in such a fiber. We then determine their spectral sensitivity to the refractive index changes of material filling the holes surrounding the core. The sensitivity is compared to that of standard FBGs photowritten in a six-hole fiber with a larger core diameter. We demonstrate an improvement of the sensitivity by two orders of magnitude and reach a resolution of 3 x 10-5 and 6 x 10-6 around mean refractive index values of 1.33 and 1.40, respectively

Assessment of the genetic diversity conservation in three tall coconut (Cocos nucifera L.) accessions regenerated by controlled pollination, using microsatellite markers

Controlled pollination process is used during the regeneration of ageing accessions in the International Coconut Genebank for Africa and Indian Ocean (ICG-AIO). The effectiveness of this process has not yet been evaluated. This study aimed to evaluate the effectiveness of controlled pollination method by investigating the level of molecular resemblance between the regenerated (G1) and parental (G0) populations of three tall coconut accessions, Mozambique Tall (MZT), Gazelle Peninsula Tall (GPT) and Tahitian tall (THT) using 15 microsatellites (SSR) markers. The results indicate a relative reduction of gene diversity during regeneration. It decreased from 0.690 to 0.587, but, low values of Jaccard’s dissimilarity index were found between regenerated and parental populations of tall coconut, varying from 0.072 to 0.133. Low values of genetic diversity between G0 and G1 tall coconut accessions (DST), ranging from 0.005 to 0.007, were recorded. Consequently, using controlled pollination technical as regeneration method of the genebank is effective for satisfying maintenance of the genetic integrity of the original coconut accessions.Keywords: Tall coconut palm, controlled pollination, regenerated accessions, genetic diversity, microsatellites markersAfrican Journal of Biotechnology Vol. 12(20), pp. 2808-281

SnO2-MOF-Fabry-Perot optical sensor for relative humidity measurements

In this paper, a new optical fiber sensor for relative humidity measurements is presented and characterized. The sensor is based on a SnO2 sputtering deposition on a microstructured optical fiber (MOF) low-finesse Fabry-Pérot (FP) sensing head. The feasibility of the device as a breathing sensor is also experimentally demonstrated. The interrogation of the sensing head is carried out by monitoring the Fast Fourier Transform phase variations of the FP interference frequency. This method substitutes the necessity of tracking the optical spectrum peaks or valleys, which can be a handicap when noise or multiple contributions are present: therefore, it is low-sensitive to noise and to artifacts signal amplitude. The sensor shows a linear behavior in a wide relative humidity range (20%–90% relative humidity) in which the sensitivity is 0.14 rad/%; the maximum observed instability is 0.007 rad, whereas the highest hysteresis is 5% RH. The cross correlation with temperature is also considered and a method to lower its influence is proposed. For human breathing measurement, the registered rising and recovery times are 370 ms and 380 ms respectively.The authors are grateful to A. Ortigosa, D. Erro, Dr. M. Bravo and Dr. R.A. Perez-Herrera. We also thank the Spanish Government projects TEC2013-47264-C2-2-R, TEC 2016-76021-C2-1-R, TEC2016-78047-R, TEC2016-79367-C2-2-R, Innocampus and the Cost Action MP 1401, as well as to the AEI/FEDER Funds

Real time measuring system of multiple chemical parameters using microstructured optical fibers based sensors

In this paper, a multiplexing system for simultaneous interrogation of optical fiber sensors which measure different parameters is presented and validated. The whole system has been tested with 6 different sensing heads with different purposes: one temperature sensing head, two relative humidity sensors and three VOCs leak sensors; all of them based on microstructured optical fibers. The interrogation system uses the FFT technique to isolate each sensor's interference, enabling their simultaneous interrogation. The system interrogates all the sensors at frequencies up to 1 KHz, showing a good performance of each measurement without crosstalk between sensors. The developed system is independent of the sensors' purpose or of the multiplexing topology.This work was supported in part by the Spanish Comisión Interministerial de Ciencia y Tecnología within projects under Grant TEC2016-76021-C2-1-R, Grant TEC2016-78047-R, and Grant TEC2016-79367-C2-2-R, in part by the Cost Action MP1401, and in part by the FEDER funds from the European Union

Conception, realization and characterization of a very high negative chromatic dispersion fiber

International audienceAfter a brief presentation ..