Xiong Yanling

Measurement of power frequency AC current using FBG and GMM

There is a potential demand for optical current instrument transformer (OCT) in power industry. In the past two decades, R&D on OCT was focused on Faraday effect based technology. As a sensing technology, Fiber Bragg grating (FBG) was more and more attractive recently. For OCT, FBG and giant magnetostrictive material (GMM) based technology will be another choice. In this paper, this kind of power frequency AC current sensing system was established. One FBG was clung on a GMM rod that was exposed to the AC current induced magnetic field. The shift of FBG reflecting wavelength was interrogated by a wavelength to amplitude simultaneous interrogation system. Experiments with and without DC bias current have been done. The relation of the sensing current and the response of the system were defined by the transfer function of the system that revealed hysteresis loop character.

A fiber grating temperature demodulator based on the tunable F-P filter

In order to improve the all kind of fiber Bragg grating (FBG) demodulation system, we make-up a fiber grating temperature demodulation system, which is consist of fiber tunable F-P filter, signal-generation, tunable voltage source and oscilloscope. The temperature signal of three FBG with different center wavelength is demodulated, and the system is demonstrated to be with sensing sensitivity of 10.47mV/°C, 10.16 mV/°C, 10.48 mV/°C. The structure of the system is very simple and easy to be realized.

The Reflection Characteristics of Thermal Regenerated Fiber Bragg Grating

The thermal regenerated grating was prepared from an ordinary single-mode fiber Bragg grating though high temperature annealing process in this paper. And the temperature characteristics and spectral properties of the thermal regenerated grating were investigated. The results show that the erasing temperature of the initial seed gratings of FBG is about 970°C and the regenerating temperature of the FBG is about 990°C. The wavelength of the thermal regenerated gratings (RFBG) exhibit excellent linear relationship with the temperature change, and the temperature sensitivity coefficient of the RFBG can get to 0.01564 nm/°C. The high-temperature sensing experiments indicate that the RFBG has a good repeatability and the optical powers of the reflection spectrum remains stable during the heating and cooling process.

The simulation of FBG demodulation system based on the tunable F-P filter

This paper implements the optical filter fiber Bragg grating (FBG) sensor demodulation system based on the tunable Fabry-Polo (F-P) filter. Paper firstly introduces the FBG sensor demodulation system block diagram; Then we uses the Optisystem software to build a virtual system and set parameters and obtain the simulation result that the optical power with the frequency has a good linear relationship; Finally we makes experimental verification finding that Simulation results are consistent with the experimental results.

FBG multiplex distance based on FMCW technology

The basic principles of Frequency Modulated Continuous Wave (FMCW) multiplexing technique addressing the distributed fiber Bragg grating (FBG) sensors were studied, and the theoretical analysis of FBG multiplex distance were carried out; In order to analyze the impact on the spectrum signal, when the FBG multiplex distance is integer or non-integer multiple of system minimum resolution distance, for the FMCW multiplexing scheme was simulated. Finally, the related experimental system was established and the results are consistent with the theory.

Alternating current sensor system using GMM

Based on the principle of FBG sensing mechanism, an alternating current sensor system, which uses a FBG attached on a magnetostrictive rod as the probe, was developed. A dynamic interrogation method was proposed based on wide band light source, by making use of the linear relationship between its power intensity and wavelength as spectrum filter. A 50 Hz AC signal is interrogated successfully through the developed system and the system transfer function was established. The amplitude and frequency of the AC signal to be measured can be well deduced through the transfer function of the system, so the alternating current measurement is accomplished.

Simultaneous thermoluminescence and thermally stimulated current in polyamide

We have obtained simultaneous thermoluminescence (TL) and thermally current (TSC) spectra in two types of polyamide film, nylons 6 and 11, to study electron detrapping and recombination. There are three main relaxation peaks or regions, designated /spl gamma/, /spl beta/ and /spl alpha/ in order of increasing temperature, in the TSC spectra. In contrast, the /spl alpha/ relaxation peak in TL spectra disappears. The centers of the peaks are located near 180 K, 230 K and 310 K, respectively. However, we also observed two anomalous phenomena: a very large, short-circuited, thermally stimulated discharge current up to 10/sup -8/ A, but reversible for non-polarized nylons 6 and 11; and no TL signals for non-poled nylon 6 films.