A Modal-Noise Insensitive Fibre-Optic Gas Sensor Arman Mohebati And Terence A King

Arman Mohebati; Terence A. King

doi:10.1117/12.961005

29 October 1989 A Modal-Noise Insensitive Fibre-Optic Gas Sensor Arman Mohebati And Terence A King

Arman Mohebati, Terence A. King

Proceedings Volume 1120, Fibre Optics '89; (1989) https://doi.org/10.1117/12.961005
Event: Sira/Fibre Optics '89, 1989, London, United Kingdom

Abstract

The performance of optical-fibre intensity sensors, particularly those utilising highly coherent diode laser sources and multi-mode fibres, is susceptible to modal-noise in the fibre. This can become a limiting factor in the sensitivity and stability of fibre-optic gas sensors based on absorption measurements where intensity variations of the order of 10^-4 need to be measured. For long lengths of fibre (several km), where natural mode scrambling in the fibre has occurred, the modal noise has been shown generally not to be a limiting factor. A signal processing scheme is proposed which is shown to reduce the performance dependence of the sensor on modal noise where short lengths of fibres are used. Data from a fibre-optic methanometer utilising this technique is presented demonstrating the improvement in the sensitivity, reproducibility and long term stability of the sensor.

Citation Download Citation

Arman Mohebati and Terence A. King "A Modal-Noise Insensitive Fibre-Optic Gas Sensor Arman Mohebati And Terence A King", Proc. SPIE 1120, Fibre Optics '89, (29 October 1989); https://doi.org/10.1117/12.961005

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