Tilted fiber Bragg grating sensors

TLDR

Optical fiber gratings are a mature technology used for sensing temperature, strain, acoustic waves, and pressure by perturbing the grating period or refractive index. This paper introduces tilted fiber Bragg gratings that couple core‑mode power into many cladding modes through a small fringe tilt. The tilt induces coupling of core‑mode light into numerous cladding modes, enabling high‑resolution refractometry, surface plasmon resonance, and multiparameter sensing. Tilted gratings multiply sensing modalities, increase resolution, eliminate temperature cross‑sensitivity and power‑source noise, exhibit high‑Q (10⁵) resonances, and support high‑resolution refractometry, surface plasmon resonance, and multiparameter sensing.

Abstract

Abstract Optical fiber gratings have developed into a mature technology with a wide range of applications in various areas, including physical sensing for temperature, strain, acoustic waves and pressure. All of these applications rely on the perturbation of the period or refractive index of a grating inscribed in the fiber core as a transducing mechanism between a quantity to be measured and the optical spectral response of the fiber grating. This paper presents a relatively recent variant of the fiber grating concept, whereby a small tilt of the grating fringes causes coupling of the optical power from the core mode into a multitude of cladding modes, each with its own wavevector and mode field shape. The main consequence of doing so is that the differential response of the modes can then be used to multiply the sensing modalities available for a single fiber grating and also to increase the sensor resolution by taking advantage of the large amount of data available. In particular, the temperature cross‐sensitivity and power source fluctuation noise inherent in all fiber grating designs can be completely eliminated by referencing all the spectral measurements to the wavelength and power level of the core mode back‐reflection. The mode resonances have a quality factor of 10 5 , and they can be observed in reflection or transmission. A thorough review of experimental and theoretical results will show that tilted fiber Bragg gratings can be used for high resolution refractometry, surface plasmon resonance applications, and multiparameter physical sensing (strain, vibration, curvature, and temperature).