Fano-like resonance in optical fiber

Fano resonances emerge from the coherent interference between a discrete resonant state and a continuum of propagating modes, giving rise to a characteristically asymmetric spectral line shape with heightened sensitivity to minute variations in the underlying physical parameters. In this study, it is provided a chronological perspective on the development and increasing implementation of Fano-type effects within fibre-optic technology. We further illustrate their implementation in fibre Bragg gratings (FBGs) through numerical simulations of resonant Fano behavior. Specifically, a Fano-like response in an FBG can be designed by introducing a tailored phase shift into the grating structure; the magnitude of this phase discontinuity constitutes an effective control parameter for tuning the interference condition and, consequently, the resulting spectral asymmetry. The resonance produces a distinctive, high-selectivity spectral response that is attractive for a broad range of photonic functionalities. Principal applications include fibre-integrated sensing, where the enhanced spectral sensitivity supports the detection of changes in refractive index, temperature, pressure, or biomolecular interactions, as well as narrowband filtering and spectral shaping for telecommunications and optical signal-processing systems.