A method of determining a strain component for a selected deformation mode of a member, comprising: propagating a light through a fiber optic cable wrapped around the member, the fiber optic cable having a plurality of sensors therein; receiving light reflected at the plurality of sensors to determine a wavelength shift of the propagated light at the plurality of sensors, wherein each wavelength shift indicates a strain on the member at a location of a related sensor; using a processor to: form a dataset (401, 403, 405) that relates the wavelength shift for the plurality of sensors to locations of the plurality of sensors at the member; perform a transform on the dataset (401, 403, 405) to obtain a spatial frequency spectrum (501, 503, 505, 507, 509), wherein a peak of the spatial frequency spectrum (501, 503, 505, 507, 509) corresponds to the selected deformation mode of the member; apply an adjustable filter (601, 603, 605, 607, 609) to the spatial frequency spectrum (501, 503, 505, 507, 509) to select a peak (701, 703, 705, 707, 709) of the spatial frequency spectrum (501, 503, 505, 507, 509) that corresponds to the selected deformation mode, wherein the adjustable filter (601, 603, 605, 607, 609) includes an index that selects the selected deformation mode; and perform an inverse transform on the selected peak to determine the strain components (801, 803, 805, 807) for the selected deformation mode. propagating a light through a fiber optic cable wrapped around the member, the fiber optic cable having a plurality of sensors therein; receiving light reflected at the plurality of sensors to determine a wavelength shift of the propagated light at the plurality of sensors, wherein each wavelength shift indicates a strain on the member at a location of a related sensor; using a processor to: form a dataset (401, 403, 405) that relates the wavelength shift for the plurality of sensors to locations of the plurality of sensors at the member; perform a transform on the dataset (401, 403, 405) to obtain a spatial frequency spectrum (501, 503, 505, 507, 509), wherein a peak of the spatial frequency spectrum (501, 503, 505, 507, 509) corresponds to the selected deformation mode of the member; apply an adjustable filter (601, 603, 605, 607, 609) to the spatial frequency spectrum (501, 503, 505, 507, 509) to select a peak (701, 703, 705, 707, 709) of the spatial frequency spectrum (501, 503, 505, 507, 509) that corresponds to the selected deformation mode, wherein the adjustable filter (601, 603, 605, 607, 609) includes an index that selects the selected deformation mode; and perform an inverse transform on the selected peak to determine the strain components (801, 803, 805, 807) for the selected deformation mode. form a dataset (401, 403, 405) that relates the wavelength shift for the plurality of sensors to locations of the plurality of sensors at the member; perform a transform on the dataset (401, 403, 405) to obtain a spatial frequency spectrum (501, 503, 505, 507, 509), wherein a peak of the spatial frequency spectrum (501, 503, 505, 507, 509) corresponds to the selected deformation mode of the member; apply an adjustable filter (601, 603, 605, 607, 609) to the spatial frequency spectrum (501, 503, 505, 507, 509) to select a peak (701, 703, 705, 707, 709) of the spatial frequency spectrum (501, 503, 505, 507, 509) that corresponds to the selected deformation mode, wherein the adjustable filter (601, 603, 605, 607, 609) includes an index that selects the selected deformation mode; and perform an inverse transform on the selected peak to determine the strain components (801, 803, 805, 807) for the selected deformation mode.