Abstract: A method of measuring strain includes providing laminated material having ply layers, and a thickness along a direction orthogonal to the ply layers, and a strain sensor embedded between adjacent ply layers, wherein: the strain sensor includes first and second planar optical waveguide, each of the waveguides having a waveguiding core defining an optical propagation direction parallel to the laminated material and a Bragg grating in the waveguiding core, the optical propagation directions of the optical waveguides being non-parallel; interrogating the first optical waveguide Bragg grating with transverse electric (TE) and transverse magnetic (TM) polarized light, to obtain a TE spectral response and a TM spectral response; interrogating the second optical waveguide Bragg grating with TE and TM polarized light to obtain a TE spectral response and a TM spectral response; and processing the TE spectral responses and the TM spectral responses to extract a through-thickness component of strain.

Abstract: A method of measuring strain comprises providing laminated material comprising two or more ply layers and having a thickness along a direction orthogonal to a plane defined by the ply layers, and comprising a strain sensor embedded between adjacent ply layers, wherein: the strain sensor comprises a first planar optical waveguide and a second planar optical waveguide, each of the first planar optical waveguide and the second planar optical waveguide having a waveguiding core defining an optical propagation direction parallel to the plane of the laminated material and a Bragg grating in the waveguiding core, the optical propagation direction of the first planar optical waveguide being non-parallel to the optical propagation direction of the second planar waveguide; interrogating the Bragg grating of the first planar optical waveguide with transverse electric (TE) polarized light and with transverse magnetic (TM) polarized light to obtain a TE spectral response of the Bragg grating for the TE polarized light and