Fibre encapsulated in stainless steel tube or short "Fibre In Metal Tube (FIMT)" is a hermetically sealed rugged construction for very long lengths of optical fibres.
The optical fibre serves as the distributed temperature sensor for LIOS DTS systems and is typically surrounded by a protective layer. It is preferably encased in a stainless steel tube which significantly increases the mechanical stability of the sensor. Furthermore, it is particularly effective in protecting against the hydrostatic pressures and corrosive environments.
FIMT constructions contain individual or multiple DTS approved fibres (single mode or multi mode, appropriate bandwidth and attenuation, phosphorus free) and are available in sizes ranging from 1 mm to 3 mm outer diameter, variations in effective wall thickness are possible as well. FIMT serves as the core for various fibre optic sensor cable constructions or may be integrated into high voltage cable designs directly.
