Researchers at the University of Pittsburgh have created an all-optical high-temperature sensor for gas flow measurements, which can operate at more than 800oC, by fusing together the concepts of active fibre sensors and high-temperature fibre sensors.
The technology is expected to find industrial sensing applications in harsh environments ranging from deep geothermal drill cores and the interiors of nuclear reactors to the cold vacuum of space missions.
The team described their all-optical approach in a paper published in The Optical Society’s journal Optics Letters. They successfully demonstrated simultaneous flow/temperature sensors at 850 C, which is a 200 C improvement on an earlier notable demonstration of MEMS-based sensors by researchers at Oak Ridge National Laboratory.
The basic concept of the new approach involves integrating optical heating elements, optical sensors, an energy delivery cable and a signal cable within a single optical fibre. Optical power delivered by the fibre is used to supply energy to the heating element, while the optical sensor within the same fibre measures the heat transfer from the heating element and transmits it back.
'We call it a smart optical fibre sensor powered by in-fibre light,' said Kevin Chen, an associate professor and the Paul E. Lego Faculty Fellow in the University of Pittsburg’s department of electrical and computer engineering.
The team’s work expands the use of fibre-optic sensors well beyond traditional applications of temperature and strain measurements. 'Tapping into the energy carried by the optical fibre enables sensors capable of performing much more sophisticated and multifunctional types of measurements that previously were only achievable using electronic sensors,' Chen said.