Fiber optic-based thermometry: evolution and development spanning five decades

Fiber Optic Sensors (FOS) have been developed since the late 1970s and amongst the earliest devices produced have been transducers for the measurement of temperature, in particular as a result of its critical importance to many industrial processes. Moving on from the original simplistic devices reported, the 1980s saw both the first use of non-linear optical techniques for distributed temperature sensing and the success of the (initially longitudinally-written) Fiber Bragg Grating – this opened up the potential of this important in-fiber device for quasi-distributed temperature sensors. Research in the field has continued now for nearly five decades and the main driver continues to be to produce a wide range optical-fiber based techniques, which can be suited to a variety of different sensor purposes, providing techniques that represent the most effective temperature measurement technology for use by industry world-wide. All this points to the value of a closer examination of the variety of approaches taken to such measurements, building on the different principles discussed. It is important to see the way those have either gone on to further success – or been largely discarded – and how the continuing need for better temperature monitoring for a number of different industries is met – and thus best served by using fiber optic techniques. This paper aims to provide such a brief overview and to point to future directions.