Patent ID: 11965732
Assignee: TOUCHNETIX LIMITED
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A method of measuring strain comprising:
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, and cladding around 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, and each of the first planar optical waveguide and the second planar optical waveguide having a thickness and a width being orthogonal dimensions perpendicular to the optical propagation direction and the width being at least an order of magnitude larger than the thickness; 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 a TM spectral response of the Bragg grating for the TM polarized light;

interrogating the Bragg grating of the second planar optical waveguide with TE polarized light and with TM polarized light to obtain a TE spectral response of the Bragg grating for the TE polarized light and a TM spectral response of the Bragg grating for the TM polarized light; and
processing the TE spectral response and the TM spectral response of the first planar optical waveguide and the TE spectral response and the TM spectral response of the second planar optical waveguide to extract at least a through-thickness component of strain within the laminated material which is aligned along the direction of the thickness of the laminated material.