Some recent advances on amplitude, wavelength, phase and polarisation modulating sensors are discussed. Although such division is general, as some recent techniques use many modulation principles simultaneously to separate efficiently the coupled parameters of interest, it still provides a basic framework for the design engineer to choose which technology may be the most appropriate for the solution of a particular problem. In cases where optical fibres rather than free-space propagating beams are used, optical fibre sensors may be divided into extrinsic or intrinsic ones. This is dependent on whether the light signal is modulated inside or outside the fibre. Examples of both extrinsic and intrinsic fibre optic sensors are given.

Inspec keywords: frequency modulation; fibre optic sensors; distributed sensors; amplitude modulation; optical modulation; intensity modulation; phase modulation; reviews; optical time-domain reflectometry; light interferometers

Other keywords: distributed sensors; polarisation modulating sensors; extrinsic fibre optic sensors; intrinsic fibre optic sensors; amplitude modulating sensors; wavelength modulating sensors; phase modulating sensors; intensity modulation; interferometric sensors; OTDR; sensor applications; self-referencing

Subjects: Fibre optic sensors; fibre gyros