SIMULTANEOUS MEASUREMENT OF STRAIN AND TEMPERATURE USING THE FIRST-ORDER AND 2ND-ORDER DIFFRACTION WAVELENGTHS OF BRAGG-GRATINGS

A method of discriminating between temperature and strain effects in f ibre sensing using a conventionally written, in-fibre grating is prese nted. The technique wavelength information from the first and second d iffraction orders of the grating element to determine the wavelength d ependent strain and temperature coefficients, from which independent t emperature and strain measurements can be made. The authors present re sults that validate this matrix inversion technique and quantify the s train and temperature errors which can arise for a given uncertainty i n the measurement of the reflected wavelength.