Community Research and Development Information Service - CORDIS


Analysis and results of experiments concerning all-fibre passive demodulation of fibre Bragg grating sensors using a many-cycle directional coupler are reported here. The principle of operation is based on the fast wavelength response of a fused tapered 2x2 directional coupler pulled through many coupling cycles. The coupler's splitting ratio is then sensitive to small changes in the reflected Bragg wavelength. A design rule to allow the selection and fabrication of a coupler with the desired response has been developed, and the coupler splitting ratio linearity with wavelength is also examined. Because such directional couplers may be readily tailor-made by choosing the number coupling cycles the coupler is pulled through during fabrication, this approach allows a range of sensitivities and wavelengths to be catered for. Problems encountered with highly-sensitive (ie fast wavelength response devices) due their polarization sensitivity are also discussed.

Additional information

Authors: KENNY R, JRC Ispra (IT)
Bibliographic Reference: Paper presented: Pacific Northwest Fibre Optic Sensor Workshop, May 7-9, 1996
Availability: Available from (1) as Paper EN 39749 ORA
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