Prospects for Fibre Bragg Gratings and fabry-perot interferometers in fibre-optic vibration sensing

Vibration monitoring of machinery is reducing the overall operating costs of industrial plants. Conventional vibration sensors, based on capacitive or piezoelectric principles, are limited in application due to the problem of electrical isolation. Fibre-optic based instrumentation is thus an attractive alternative method of vibration measurement in the vicinity of electrical substation. This paper discusses several techniques of vibration sensing using optical fibre technology and assesses their potential for use on electromechanical equipment. Firstly an overview of sensor based on In-Fibre Bragg Gratings is presented, and its potential for the measurement of strain and vibration is assessed. Secondly, vibration sensing using fibre-optic intensity-based measurement is presented and then Fabry-Perot Interferometer (FPI) for vibration sensing is critically reviewed. Of these, the FPI is the most attractive since it can easily be configured within a reflective fibre-optic probe. However, reported FPI sensors have been highly sensitive to measurement errors caused by mechanical vibration, temperature, and acoustic waves. This paper reviews technological developments of FPI to vibration sensing in extreme electromechanical environments and also for non-contact measurement. Finally this paper presents an overview of dual-wavelength technique for assessment of vibration signature. (C) 2004 Elsevier B.V All rights reserved.