Bragg fibre sensors

In the optical sensing community, there has been intense interest in the interaction of light with both itself and matter for sensing of measurand-induced environmental changes. Smart sensing is a recent and fast growing field of optical metrology and is closely linked to the field of structural health monitoring, which is typically imple- mented using optical fibre sensors. Fibre Optic Sensors (FOS) exhibit significant advantages over conventional electro-mechanical sensors such as high electromagnetic immunity,measurement of a wide range of measurands, small size and high sensitivity.

Ideally, these sensors would be accompanied by a series of actuators to allow a structure to compensate or correct for any changes in position, strain or temperature which deviate from its position of equilibrium. Fibre Bragg gratings (FBG) represent a key element in the field of optical fibre sensors. From the earliest stage of their development, fibre Bragg gratings have been considered for use as sensor elements capable of providing quasi-distributed sensing, suitable for measuring static and dynamic fields such as temperature, strain and pressure.

They have become an important component in the development of smart structure technology. The key advantage of fibre Bragg gratings over other optical fibre sensors is that the measurand is directly encoded in the reflected wavelength. Since the wavelength is an absolute parameter, the signal returned from the FBG can be processed such that its information remains immune to power fluctuations along the optical path. In addition, gratings can be written using a variety of inscription methods at well defined wavelengths. They can operate over application-specific ranges making them most suitable to wavelength division multiplexed (WDM) approaches. As such any interrogation system should be compatible with multiplexing,so as to reduce costs and take advantage of the suitability of these sensors for quasi-distributed sensing.

For more details on the techniques developed for interrogation of FBGs, please follow the links on the individual researchers webpages.