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The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of Open Access research papers by University of Strathclyde researchers, including by researchers from the Department of Computer & Information Sciences involved in mathematically structured programming, similarity and metric search, computer security, software systems, combinatronics and digital health.

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A novel fiber-optic intra-cavity sensing network using a mode-locked fiber ring laser

Yu, H.D. and Jin, W. and Liao, Y. and Stewart, G. and Culshaw, B. and Ho, H. and Li, Y. (2002) A novel fiber-optic intra-cavity sensing network using a mode-locked fiber ring laser. In: 15th Optical Fiber Sensors Conference, 2002-05-06 - 2002-05-10.

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A promising method for high sensitivity gas detection is intra-cavity spectroscopy [l] where the gas absorber is placed directly within a laser cavity. The high sensitivity arises from the very large number of passes through the gas cell within the cavity, effectively transforming a short absorption cell into a highly efficient multi-pass system. As a consequence a weak gas absorption line can have an enormous impact on the laser output. Recently intra-cavity spectroscopy with fiber lasers has attracted considerable attention [2,3,4]. An all-fiber intra-cavity laser system can use the mature passive and active fiber components from the communications market with compact micro-optic gas cells, allowing safe, remote and continuous gas monitoring. Additionally, fiber laser sources have a broad gain bandwidth, such as the erbium-fiber laser with gain over 1530-1580nm, and thus can be used as a source for a multi-gas sensor avoiding the cost of individual (DFB) lasers for each gas. However the high cost of the active fiber components such as the Erbium-Doped Fibre Amplifier (EDFA) would also limit the commercial application of single point measurements with intra-cavity fiber spectroscopy. Ideally an intra-cavity system would be capable of making multi-point measurement of several gases within the gain spectrum of the erbium doped fibre laser. A multiplexed network would greatly reduce the cost per point by sharing the same fiber source and the same signal-processing unit. In this paper, we present a system that combines a mode-locked fiber ring laser with intra-cavity spectroscopy to distinguish between different gas cells in a ladder sensing network. The system outputs strong pulsed lasing signals only when certain matching conditions are satisfied [5] and individual sensors are addressed by different frequencies of the mode-locked fiber ring laser.