Tilted short-period fibre-Bragg-grating-induced coupling to cladding modes for accurate refractometry

Abstract

We investigate the changes in the transmission spectrum of long period fibre gratings and tilted short-period fibre Bragg gratings versus the refractive index of the surrounding medium. The metrological characteristics of tilted short-period fibre Bragg gratings and an analytical method enabling their potential use in accurate refractometry are discussed.

Запись И Визуализация Волоконных Решеток Показателя Преломления С Наклонными Штрихами

“…Эта особенность позволяет использо-вать НВБР при изготовлении сглаживающего эрбиевого усилителя [6], оптического анализатора спектра [7], фильтра ввода-вывода [8]. Другая особенность НВБР -они чувствительны к показателю преломления внешней среды, что позволяет использовать их при изготовле-нии рефрактометров [9][10][11] и измерителей концентра-ции [12,13]. НВБР, имеющие относительно большой угол наклона, обладают высокой чувствительностью к состоянию поляризации проходящего света.…”

Near-Field Nanofluid Concentration Measurement by Rayleigh Particle Scattering Bragg Grating Evanescent Wave

“…Since fiber optic sensors demonstrate small size, light weight, high resolution, immunity to electromagnetic interference, harsh environment operational capability, etc., many types of designs have been constructed and developed. Periodic structure grating-type fiber sensors, including long period grating (LPG), [21] tapered grating, [22] sampled FBG, [23] tilted FBG, [24,25] D-type FBG, [26] partial thinned FBG, [27,28] total uniform thinned FBG, [29,30] etc., were used to measure the RI and the concentration of the fluid without any nanoparticles. The basis of sensing principle and designing method based on the fiber sensors is similar and relies on the change of the evanescent field exposed in the surrounding medium.…”

Temperature and strain discrimination using a single tilted fibre Bragg grating

“…The cladding mode resonance wavelengths will be sensitive to differential changes in the indices of the cladding and core modes, which have been exploited previously to demonstrate a refractometer [16]. For a small tilt angle, it is possible to produce a well defined single loss band that is blue shifted with respect to the main Bragg feature [17], as shown in figure 2.…”