Na Chen

Highly Sensitive Liquid-Level Sensor Based on Etched Fiber Bragg Grating

A highly sensitive liquid-level sensor based on etched fiber Bragg grating (FBG) is proposed and demonstrated. The transmission dips of FBG spectra are affected by the fraction of the length of the etched FBG that is surrounded by the liquid. The experiments show that for a liquid-level variation of 24 mm, the transmission dip difference changes about 32 dB. Also in the linear region, a high sensitivity of 2.56 dB/mm is achieved.

Cladding mode resonances of etch-eroded fiber Bragg grating for ambient refractive index sensing

In this Letter, the cladding mode resonances of a chemical etch-eroded fiber Bragg grating are proposed for highly sensitive ambient refractive index sensing. The varying characteristics of several different order cladding mode resonances with ambient refractive index are explored experimentally. The maximum sensing sensitivity of 172nm∕riu for the third-order cladding mode resonance is achieved in the experiments. Under the same cladding diameter, the cladding mode resonances have narrower bandwidth and response much more sensitive to the ambient refractive index changing than conventional Bragg core mode resonance, which would enable them to achieve a higher resolution.

Theoretical and experimental study on etched fiber Bragg grating cladding mode resonances for ambient refractive index sensing

The theoretical model of etched fiber Bragg grating (FBG) backward cladding-mode resonances for ambient refractive index sensing is presented. The dependent behaviors of the mode resonances have been analyzed in the etching process and the ambient refractive index changed. The analysis is based on the classical coupling-mode theory while considering interactions among multiple modes and developed on a three-layer step-index fiber geometry. Experimental data match the theoretical model wonderfully. This model not only describes the relationship between the FBG backward cladding-mode resonances and the ambient index but also is valuable for the design of a flexible highly sensitive ambient index sensor.

Characterization of a high birefringence fibre Bragg grating sensor subjected to non-homogeneous transverse strain fields

Several theoretical and experimental studies have been carried out in recent years to characterize the spectral response of an optical fibre Bragg grating (FBG) subjected to non-homogeneous axial strain fields. However, few works have considered the evolution of the spectrum when a FBG fabricated in a high birefringence fibre is subjected to non-homogeneous transverse loading. In this paper, a physical model is described and a numerical simulation based on the piecewise-uniform approach is also used to calculate the response of a FBG fabricated in a high birefringence fibre under some typical non-homogeneous transverse strain fields. Finally, simulated results are analysed and compared with a FBG fabricated in a conventional monomode fibre.

Use of Fiber Bragg Grating Sensors for Determination of a Simply Supported Rectangular Plane Plate Deformation

A measurement method has been developed to determine the full-field deformation of a simply supported plane plate under transverse load. The method utilizes strain information provided by a set of four fiber Bragg grating sensors mounted on the plate in a way that all sensors measure strains along one certain direction. The sensors were interrogated using a wavelength swept fiber laser. Utilizing the strain information and the first four terms of Navier solution of simply supported rectangular plate, the necessary parameters for determining the deflection could be computed. By substituting the values of x- and -y- coordinates of each position on the rectangle plate, the full-field deformation information can be obtained. Single-point loading tests were experimentally performed to verify the accuracy of the method.

Fiber Bragg grating cladding mode resonance liquid-level sensor

A Fiber-optic liquid-level sensor based on etched fiber Bragg grating (FBG) cladding mode resonance is proposed and demonstrated both theoretically and experimentally. The theoretical model of the FBG cladding mode liquid-level sensor is built under a three-layer step-index fiber geometry. Response of cladding mode resonance spectra to the variation of ambient liquid level are studied and simulated numerically with couple mode theory and transmission matrix method. In the experiments, a chemical etching method is adopted to diminish the fiber cladding diameter and increase the sensitivity of cladding mode resonances to the ambient refractive index change. Dependences of FBG cladding mode resonance spectra on the liquid-level variation are measured and the experiments data match the model well.