Bragg gratings interrogating system using MEMS and optical circuits

It is well documented that optical sensors offer many advantages over conventional electronic devices for some applications because they are more versatile,lighter,smaller,immune to electrical interference and can be densely multiplexed. However, to date, many optical sensor instrument systems have been insufficiently robust for use in harsh environments and relatively expensive due to the use of discrete optical components. Hence the primary aim of this work is to develop a physically robust and cost effective interrogation system for fibre Bragg grating strain sensors by integrating a system on a silicon chip. Therefore it will be possible to replace many of the costly discrete components. Related improvements will be the reduction of size and weight,an increase in robustness, and performance in relatively harsh environments. This work will focus on the development of a Micro Electro Mechanical System (MEMS) tunable Fabry-Perot optical filter, together with integrated optical circuit fabricated on silicon-on-insulator (SOI) to deliver the signal to the Bragg gratings and to detectors based in the same optical circuit. In this paper we discuss the requirements for integration, as well as reviewing the principles of strain measurement using fibre Bragg gratings. The latter will include a brief discussion of the merits of multiplexing via single or multiple fibres.