Temperature independent bend measurement using a pi-phase shifted FBG at twice the Bragg wavelength

The effect of bending on the twin peaks of an alternative type of pi-phase shifted fibre Bragg grating (FBG) (embedded in a resin) at twice the Bragg wavelength, has been investigated. Variation of the direction of bending resulted in corresponding changes in the relative intensity of these peaks. Temperature independent bend measurements were realised by monitoring the change of ratio of the reflected intensities of these peaks