Application of non-uniform strain to discrete segments of a fiber grating mechanically changes the structure type of the associated device, e.g., the refractive index perturbation profile of the fiber grating is changed from uniform to phase shifted superstructured, or from chirped to superstructured. The strain may be applied with one or more deformable corrugated slides which are bonded to the fiber grating between the discrete segments. The applied strain changes the local period of fiber grating. Complex changes may be achieved via variations of corrugated slide dimensions. An LPFG may be provided with bare fiber by applying periodically longitudinal axial strain to fiber at multiple discrete segments on the fiber.