Development of gas detection systems based on microstructured optical fibres

• Type: Thesis
• Date: 2008

Authors

Filipe Magalhães (Author) FEUP; Henrique Salgado (Technical adviser) FEUP

Scientific classification

FOS: Engineering and technology > Electrical engineering, Electronic engineering, Information engineering

CORDIS: Technological sciences > Technology > Optronics ; Technological sciences > Technology > Computer technology > Signal processing ; Technological sciences > Engineering > Electrical engineering ; Physical sciences > Physics

Associated Institutions

FEUP - Faculdade de Engenharia da Universidade do Porto

Other information

Abstract (EN): The main goal of this project was to study and develop sensing systems for the remote detection of gases with the use of microstructured optical fibres of the hollow-core type (HC-PCF) and the use of signal processing techniques usually associated with absorption spectroscopy. After studying the common methodologies for this type of monitoring many drawbacks were identified, among which were the need for long interaction path lengths and high sampling volumes, the need for precise alignments and optics and the sensitivity to power fluctuations. Photonic Crystal Fibres (PCF) arose as an exceptionally interesting player in the field of gas sensing since they promote the creation of short and direct interaction paths between light and gas and can be tuned to address any specific gas. Thus, their principle of operation and main optical properties were studied and described. The diffusion time of gases inside of microstructured fibres is a subject of special importance if we intend to use these fibres as sensing heads. As a consequence of its theoretical study and experimental analysis, fruitful results for the planning of a new configuration for the sensing head were achieved. Light coupling between standard optical fibres and hollow-core photonic crystal fibres is a practical issue that was also evaluated in the aim of the work here presented. The splice between these two types of fibres was also optimized. Wavelength Modulation Spectroscopy is a powerful and sensitive technique for gas detection given that detection is shifted to frequencies far from the base-band noise, improving the signal-to-noise ratio. Consequently, it was the chosen signal processing technique to be used in the implementation of an experimental setup for the detection and monitoring of a specific gas species. The implementation of a portable and compact unit for remote gas monitoring, involving several of the aspects here approached, has already been initiated.

Language: Portuguese

Type (Professor's evaluation): Scientific

No. of pages: 98