Development of fibre Bragg grating based strain/temperature sensing system

We have characterised a strain and temperature sensing system being developed by Southern Photonics that uses a new Optical Interrogator and fibre Bragg gratings. We have determined the key strain and temperature coefficients, and shown that strain and temperature can be measured simultaneously. The experimental uncertainty is 5.2 pm when using the 1540 nm fibre Bragg grating, which corresponds to an experimental uncertainty in measuring the temperature of 0.54 ºC and in measuring the strain of 3.4 με. Simulations predict that a Bragg reflection of more than 90% can be achieved for Bragg Gratings in polymer thin films containing chromophores for grating lengths as small as 200 μm. A small Bragg grating length means that it should be possible to create waveguides and four Bragg gratings for strain tensor and temperature measurements within an area as small as 5×5 mm2.