The tilted fiber Bragg grating (TFBG) is a new kind of fiber-optic sensor that possesses all the advantages of well-established Bragg grating technology in addition to being able to excite cladding modes resonantly. This device o. The tilted fiber Bragg grating (TFBG) is a new kind of fiber-optic sensor that possesses all the advantages of well-established Bragg grating technology in addition to being able to excite cladding modes resonantly. This device opens up a multitude of opportunities for single-point sensing in hard-to-reach spaces with very controllable cross-sensitivities, absolute and relative measurements of various parameters, and an extreme sensitivity to materials external to the fiber without requiring the fiber to be etched or tapered. Over the past five years, our research group has been developing multimodal fiber-optic sensors based on TFBG in various shapes and forms, always keeping the device itself simple to fabricate and compatible with low-cost manufacturing. This paper presents a brief review of the. ••A review of the principle, fabrication, characterization, and implementation of TFBGs have been presented.••The progress in TFBG sensing applications with special emphasis on mechanical sensing for structural health monitoring and biochemical sensing for in-situ medical detections have been reviewed.••The future development of TFBG sensors with efforts of multidisciplinary collaboration has been discussed for advanced and practical sensing tools using optical fibers.PhotonicsOptical fiberGratingBraggMechanical sensingBiochemical sensingThe field of optical fiber technology has experienced an interesting return towards its sources over the past few years. Because of the need for ever increasing communication capacity, transmission systems based on multimode optical fibers are being developed for mode multiplexing applications,,,. The same is true for optical fiber sensors where there is a growing interest in using the simultaneous but differential response of optical fiber modes to perturbations as a means of increasing the sensitivity, capacity, or limits of detection (LOD) in sensing systems,. In order to access these improved functionalities however, some form of mode control is required. While complex mode launching instrumentation based on free space optics can be used in telecommunications, suc. 2.1. FabricationTFBGs are fabricated using the same tools and techniques as standard FBGs, i. e. from a permanent refractive index change induced in doped glasses by an interference pattern between two intense ultraviolet laser beams, or a point by point approach. In general however, the phase mask technique,,, is preferred for mass produced FBGs. In this case, the interference pattern is generated by a diffractive phase mask located in close proximity to the fiber. The period of the grating is fixed by the phase mask and because of the proximity of the fiber, low coherence ultraviolet sources can be used, such as high energy pulsed excimer lasers. With a phase mask, tilting can be done in two ways: rotating the ph.
