André Fougères

Distributed fibre optics polarimetric chemical sensor

A new distributed fibre optic chemical sensor based on evanescent wave polarimetric interferometry is proposed with the underlying objective to apply the technology to gas chromatography. It allows real-time monitoring of the displacement of a chemical substance along a capillary. Theoretical analysis, modelling and fabrication of a special fibre containing an off-axis capillary is presented. Proof of the principle is experimentally demonstrated with liquid droplets.

Vapor zone velocities measurement using a capillary optical fiber sensor with an application to gas chromatography

A fiber optic sensor has been used for real-time measurement of the migration rates of all the compounds in a mixture separated by gas chromatography. The sensor makes use of a coated capillary optical fiber as the column. This new type of waveguide consists in a polarization-maintaining optical core positioned close to the capillary edge along the entire fiber length. The optical detection is performed through the coupling of the two polarization modes of the waveguide and this coupling is detected by a polarimetric interferometry technique. Through some signal processing, the resulting interferogram provides the migration rates of the various compounds of a gas mixture flowing in the capillary. One of the major benefits of this optical migration rate sensing is that the detection of each velocity peak appears as soon as the analyte enters the capillary fiber and the peaks are constantly measured during the whole separation process. Carrier gas acceleration occurring in the column is plainly demonstrated. This paper presents a proof-of-concept on a qualitative basis. The experiments were done at 29 degrees C because the current opto-fluidic set-up cannot withstand a higher temperature.

Combined fibre-optic sensor for colour and refractive index (CI) monitoring

Two fibre-optic probes are combined for the simultaneous monitoring of colour and refractive index of liquids, including highly coloured ones. It is shown how, through modelling, the design can be adapted to cover different ranges of refractive index, light absorption and sensitivity.

Ethanol concentration measurement by Raman spectroscopy in liquid-core microstructured optical fiber

A liquid-core air-clad microstructured fiber has been developed for determination of ethanol concentration in aqueous solutions by Raman spectroscopy. The sensor shows a linear response and a low ethanol concentration solution has been characterized using the calibrated sensor. The configuration used for light and liquid injection is stable and robust, making the sensor useful for on-line measurements.

Detection of high-PMD sections along installed fibers by means of a polarization OTDR

We present the methodology and the results from field measurements along installed fiber links on the localization and classification of fiber sections with respect to their polarization-mode dispersion (PMD) characteristics using a polarization sensitive OTDR (P-OTDR). The technique relies on the statistical analysis of the local degree of polarization (DOP) obtained from the backscattered signal. It allows classifying fiber sections as low-, medium- and high-PMD contributors.

Industrial site particulate pollution monitoring with an eye-safe and scanning industrial fiber lidar

12 Over the past few years, INO has developed an Industrial Fiber Lidar (IFL). It enables the particulate pollution monitoring on industrial sites. More particularly, it has been used to take measurements of particulate concentration at Port Facilities of an aluminum plant during boat unloading. It is an eye-safe and portable lidar. It uses a fiber laser also developed at INO emitting 1.7 microJoules at 1534 nm with a pulse repetition frequency of 5 kHz. Given the harsh environment of an industrial site, all the sensitive equipment like the laser source, detector, computer and acquisition electronics are located in a building and connected to the optical module, placed outside, via optical fibers up to 500 m long. The fiber link also offers all the flexibility for placing the optical module at a proper location. The optical module is mounted on a two axis scanning platform, able to perform an azimuth scan of 0 to 355 deg and an elevation scan of +/- 90 deg, which enables the scanning of zones defined by the user. On this industrial site, materials like bauxite, alumina, spathfluor and calcined coke having mass extinction coefficients ranging from 0.53 to 2.7 m2/g can be detected. Data for different measurement configurations have been obtained. Concentration values have been calculated for measurements in a hopper, along a wharf and over the urban area close to the port facilities. The lidar measurements have been compared to high volume samplers. Based on these comparisons, it has been established that the IFL is able to monitor the relative fluctuations of dust concentrations. It can be integrated to the process control of the industrial site for alarm generation when concentrations are above threshold.

Fiber optical chemical sensors: design, fabrication, and characterization of a multimode plastic optical fibre with an ion-selective cladding

Multimode PMMA optical fibres with a cladding made from ion-selective membrane were designed, prepared, and investigated. Some were prepared by direct drawing of membrane-coated preforms and others were overcoated. Results obtained indicate loss of membrane sensitivity that is attributed to decrease of its ionic permeability. Absorbance of the fibre follows a modified Beer law as confirmed by rank analysis of series of spectra and explained by significant mode coupling within the fibre.