We propose a novel method for multiple parameters and phase reconstruction of a chirped Fiber Bragg Grating (FBG) through two thermally-modulated reflection intensity spectra and genetic algorithm. Two temperature distributions are used to modulate the chirped FBG’s intensity spectrum in order to synthesize FBG’s parameters through a genetic algorithm. Thus, the phase response can be reconstruc...

In strain measurement applications, the matched fiber Bragg gratings (FBG) method is generally used to reduce temperature dependence effects. The FBG parameters have to be designed to meet the requirements by the particular application. The bandwidth and slope of the FBG has to be balanced well, according to the measurement range, accuracy and sensitivity. A sensitivity enhanced strain demodula...

This study proposes an improved bonding method for attaching a fiber Bragg grating (FBG) on surface of a structure to measure its dynamic strains. The improved bonding fiber Bragg grating is called IBFBG for short in this study. The bonding method provides the chance to let the IBFBG and resistance strain gauge measure the longitudinal strain at the same point. This study use two steel cantilev...

A fiber Bragg grating (FBG) vibroacoustic sensor exploiting an intensity-based interrogation principle is presented. The optical system is complemented by signal processing techniques that allow disturbances to be mitigated and improve the spectral estimation. The sensor is capable of performing frequency analysis of sounds up to 3 kHz, with top sensitivity in the 100-500 Hz frequency range, an...

The spectral response of the uniform FBG with different grating parameters such as grating length and index change are provided and discussed. The coupled mode theory is a suitable tool for analysis and obtaining quantitative information about the spectrum of a fiber Bragg grating. The coupled mode equations can be obtained and simplified by using the weak waveguide approximation. The spectrum ...

This paper presents the feasibility of utilizing fiber Bragg grating (FBG) and long-period fiber grating (LPFG) sensors for nondestructive evaluation (NDE) of infrastructures using Portland cement concretes and asphalt mixtures for temperature, strain, and liquid-level monitoring. The use of hybrid FBG and LPFG sensors is aimed at utilizing the advantages of two kinds of fiber grating to implem...

The ability to tune the Bragg wavelength of a fibre-Bragg grating (FBG) in an all-fibre laser can offer added functionality such as laser wavelength tunability, polarization selectivity, and Q-switching. Compared to current techniques which rely on mechanically straining the FBG to achieve Bragg-wavelength tunability, an all-optical technique for tuning an FBG offers potentially faster switchin...

A fiber-optic vector vibroscope based on orthogonal polarization cladding-to-core recoupling is demonstrated. A compact structure in which a short section of polarization-maintained (PM) fiber stub containing a straight fiber Bragg grating (FBG) is spliced to another single-mode fiber. Two well-defined orthogonally polarized cladding modes reflected by the PM-FBG are recoupled at the junction a...

For the first time, Fiber Bragg grating (FBG) structures have been inscribed in single-core passive germanate and three-core passive and active tellurite glass fibers using 800 nm femtosecond (fs) laser and phase mask technique. With fs peak power intensity in the order of 10(11)W/cm(2), the FBG spectra with 2nd and 3rd order resonances at 1540 and 1033 nm in the germanate glass fiber and 2nd o...

A reflection fiber inclinometer is proposed and experimentally demonstrated based on two linearly polarized (LP) modes coupling. The configuration consists of a section of polarization-maintaining fiber (PMF) containing a fiber Bragg grating (FBG) splicing with single mode fiber (SMF). Bending the PMF in the upstream of FBG can induce an additional birefringence of PMF, which results in the int...