基于光纤光栅的钢板拉伸应变监测研究

光纤布拉格光栅(FBG)是一种国际上新兴的在光纤通信、光纤传感等光电子技术领域有着广泛应用前景的基础性光纤器件。本文首先介绍FBG传感原理,然后用光纤布拉格光栅应变传感器和高精度电阻应变片同时监测钢板拉伸应变变化,并对实验获得的数据进行分析。结果表明FBG应变传感器测得的应变和高精度应变片测得的很接近,反射波长和应变具有很好的相关性,相关系数达到0.9995。基于光纤布拉格光栅的应变测方法可行,并具有良好的应用前景。

A novel temperature-insensitive strain sensor based on tapered fiber grating

A novel temperature-insensitive strain sensor based on bandwidth demodulation of the reflected light from the tapered fiber grating is presented, which is simple and low-cost and has considerable potential particularly application for strain sensing,and with the development of the interrogation system, it can demodulate both the bandwidth and the center wavelength of the reflected light from TFG to measure strain and temperature simultaneously.

Study of a high-temperature and high-pressure FBG sensor with Al_2O_3 thin-wall tube substrate

A fiber Bragg grating(FBG) high-temperature and high pressure sensor has been designed and fabricated by using the Al2O3 thin-wall tube as a substrate.The test results show that the sensor can withstand a pressure range of 0-45 MPa and a temperature range of -10-300 ℃,and has a pressure sensitivity of 0.0426 nm/MPa and a temperature sensitivity of 0.0112 nm /

Analysis of a FBG sensing system with transverse uniform press by using genetic algorithm

An analytical method in a quasi-static fiber grating sensing system under transverse uniform press is proposed based on genetic algorithm The effect of population size, generations, crossover ratio and mutation ratio to genetic algorithm, and the optimization parameters of genetic algorithm were given. The relevant experimental system is constructed. The simulation and experiments show that the analytical method proposed can be applied to analyze the reflective spectra of the quasi-static FBG sensing system at transverse uniform press, the strain measurement with high-precision of 0.91% can be

Influence of stress birefringence on the performance of a FBG pressure sensor

The effects of using overall affix and two-spot affix between the FBG and underlay on the characteristics of the pressure sensors are compared both experimentally and theoretically.It is found that overall affix can produce large nonlinear effect on the characteristics of output of the sensors.The nonlinear effect caused by the expanded spectral width mainly due to the stress birefringence and the stress grads etc.The experimental result shows that the spectral width caused by using overall affix is 0.28 nm and the linearity can have up to 1.89% of increasing by using two-spot affix.The method of two-spot affix can improve response characteristics of the sensor which is benefit to achieve wavelength demodulation and to improve measurement precision.

Switchable dual-wavelength erbium-doped fiber laser with a tilted fiber grating

A dual-wavelength erbium doped fiber laser with a tilted fiber Bragg grating and photonic crystal fiber is proposed and demonstrated. In the laser, a 2W EDFA provides gain for all the laser lines; the highly nonlinear photonic crystal fiber introduces dynamic energy transfer between the two wavelengths caused by four wave mixing effect, so that a stable dual- wavelength oscillation at room temperature is implemented. Different switching modes can be achieved by adjusting the lateral offset between the fiber grating and the guiding single mode fiber or by varying the state of polarization in the laser cavity. The maximum of output power of the laser has reached 314mW.

Application of genetic algorithm in quasi-static fiber grating wavelength demodulation technology

A modified genetic algorithm (GA) has been proposed, which was used to wavelength demodulation in quasi-static fiber grating sensing system. The modification method of GA has been introduced and the relevant mathematical model has been established. The objective function and individual fitness evaluation strategy interrelated with GA are also established. The influence of population size, chromosome size, generations, crossover probability and mutation probability on the GA has been analyzed, and the optimal parameters of modified GA have been obtained. The simulations and experiments, show that the modified GA can be applied to quasi-static fiber grating sensing system, and the wavelength demodulation preci- sion is equal to or less than 3 pm.

Analysis of photonic crystal fiber sensor character

The special character of a PCF which is used as a gas or liquid sensor is discussed. The field distribution is analyzed when the solid core PCF is injected with different medium that has different relative dielectric constant(or refractive index) . And the experiential formulas of the relation between refractive index of some kinds of liquid and their concentration are given,in order to measure the concentration of the relative liquid. At the same time,the effect of propagation constant on PCF sensor character is also discussed. Furthermore,the photonic band-gap(PBG) of PCF(PBG-PCF) is calculated at different medium relative dielectric constant,when it is injected with different medium. That is the principle basis for this kind of PCF sensors.

Experimental study on an all-optical switching based on MF-NOLM

在这篇论文，所有光的切换的实验基于微观结构纤维(MF ) 被报导非线性的光环镜子(NOLM ) 。在实验， 25-meter-long MF (纬= 36W ? 1km ? 1 @ 1550 nm )当非线性的光循环镜子和输入信号的非线性的媒介被 10 GHz 悦耳的微微秒激光来源产生，被使用，与一在 2 ps 的一半最大值( FWHM )完整宽度、在 1550 nm 集中。随输入力量的增加，蟺非线性的阶段移动被 40/60 coupler 在实验获得，但是一样的结果不能被 48/52 coupler 发现。另外，切换的设备能也被用作一个所有光的新生。CLC 数字 TN253 文件代码 A 这个工作被中国(2003CB314900 ) 的国家基本研究节目支持，中国教育部(号码 104046 ) 的关键资助工程和公民中国(2003AA311010 ) 的 863

Investigation of all-optical regeneration based on self-phase modulation in microstructured fibers

All-optical regeneration based on self-phase modulation in microstructured fibers is studied. The effects of pulse peak power into the fiber, pulse width and filter parameters on the performance of the regenerator are investigated. The effects of normal dispersion and anomalous dispersion of the microstructured fiber on optical regeneration are compared. The nu- merical results show that optical regeneration can be achieved by using microstructured fibers with normal dispersion or anomalous dispersion, but the normal dispersion decreases the oscillatory structure in the broadened spectra and obtain a better regenerator transfer function. In order to achieve optical regeneration, the input peak power into the microstructured fiber and the filter parameters need to meet certain requirements. By optimizing those parameters, a better regeneration result can be obtained.

Novel intra-cavity self-organization coherent erbium-doped fiber laser

A novel all-fiber self-organization coherent Erbium-doped fiber laser is proposed and demonstrated. The laser system is composed of two independent lasers. When each of the two branch lasers operates independently, the output power is 10. 41mW and 8.69 mW respectively. By adjusting a polarization controller (PC), the two lasers achieve coherent coupling, and the output power is 24.4 mW, which is more than two times that the single laser yields. Furthermore, we bring forward and discuss the factor estimating the effect of coherent combination—coherent coupling factor. The value of growth factor to evaluate the effect of coherent combining is 1.27. The coherent fiber laser has the advantages of simple structure, high efficiency and single frequency, which conduce to coherent coupling easily.

A new setup to tune the center wavelength of FBGs

A novel opening loop structure of fiber Bragg grating is proposed.From the analysis of the strain distribution at the side of the opening loop we found that the structure can be used as a new setup to linearly tune the central wavelength of the fiber Bragg gating.The setup is an uniform fiber Bragg grating bonded to the side of a beam which can produce an uniform strain.The experimental results show that the wavelength range of linear tuning is about 5.0 nm,the sensitivity is about 3.18 nm/N and the linearity is up to 0.998 8.The largest tuning range of the setup is about 11.0 nm while the linearity is 0.994 1 in the range of 0 and 11.0 nm.Experimental results are in good agreement with our theoretical analysis.

Reproducibility of splicer-based long-period fiber gratings for gain equalization

We fabricated long-period fiber gratings(LPFGs) using electric arc discharges. We observed that the fiber becomes slightly tapered due to longitudinal tension during the arc:this effect depends on the arc current and time length. We experimentally investigated how these characteristics can influence grating's performances,especially in view of employing the LPFG as gain equalizer for an erbium-doped optical amplifier. As expected,we found that the spectral response of the grating depends on the period Λ,the intensity of the perturbation,the grating length and the type of mode-coupling induced. Since this last parameter cannot be estimated directly from the transmission spectra,we propose a method to determine the mode-coupling occurring in the device and to assess the index modulation induced by the electric arcs. This method combines both experimental and simulated data,and can be used to characterize LPFGs made-up by any method.

Design of supercontinuum source for coherent anti-Stokes Raman scattering microscopy

A new method to obtain supercontinuum(SC) source for multiplex coherent anti-stokes Raman scattering (CARS) microscopy is proposed. The nonlinear propagation in photonic-crystal fibers (PCF) of femtosecond pulse laser with central wavelength at 800.9 nm is studied with scalar wave theory. Based on the incident laser power and dispersion of PCF, super broadband source for multiplex CARS microscopy is designed.

Linearity optimization of edge filter demodulators in FBG_s

A kind of electric circuit is improved to optimize the linearity of edge filter demodulators in FBGs.By using a logarithm amplifier and an extraction operation,the linear range of optimized edge filter demodulators has been broadened effectively,and the requirement of optical filter's linear range has been reduced. Theoretical analyses and the simulation results indicated that the linear range of optimized edge filter demodulator's covers the whole transition region of the edge filter,while a strict linearity of the optical filter is not necessary.

Investigation on reflection spectr a of chirped and phase-shifted fiber Bragg gratings

The characteristics of chirped and phase-shifted fiber Bragg gratings have been investigated by the use of transfer matrix formulation. While the characteristics of a chirped and phase-shifted fiber Bragg grating are the same as those of non- chirped one in some important aspects, both the reflection and transmission windows of a chirped and phase-shifted fiber Bragg grating can be broadened in a wide range. Therefore, chirped and phase-shifted fiber Bragg gratings will have applications in WDM or DWDM optical communication systems. The work in this paper can be used to design the new devices based on chirped and phase-shifted fiber Bragg gratings.

S-band gain flattened distributed fiber Raman amplifier with chirped fiber bragg grating filter

S-band gain flattened distributed fiber Raman amplifier with a bandwidth from 1 488 nm to 1 541 nm(53 nm in width),an averaged gain of 10 dB and a gain ripple of ±0.6 dB is obtained successfully,in which a single-wavelength high power fiber Raman laser with wavelength of 1 427.2 nm is used as the pump and the chirped fiber Bragg grating is used as the gain flattening filter.Besides,filter wavelength division multiplexer(FWDM) is used as the multi-signal multiplexer and 1 427 nm/1 505 nm coarse wavelength division multiplexer(CWDM) is used as the pump-signal coupler.The gain media are G652 fiber of 50 km in length and dispersion compensation fiber(DCF) of 5 km in length.Moreover,the location arrangements of different type of fibers and the effect caused by gain flattening filter as well as their solutions are discussed in detail.It is very significant to extend the range of optical fiber communication band and increase the capacity of fiber communication especially for ultra-long haul and ultra-high capacity communication system.

Multi-wavelength fiber laser based on broadband fiber grating and HiBi fiber loop mirror

A fiber laser based on broadband C-band fiber grating (CFG) and high birefringence (HiBi) fiber loop mirror (FLM) is demonstrated, which uses the comb-like reflection performance of the HiBi FLM. Under different polarization states, different output lasers are gained by choosing the polarization states of the light in the cavity using the polarization controller. By this method, a single wavelength or dual wavelength laser beam can be output, and multi-wavelength oscillates can be achieved.

Principles and realizations of FBG wavelength tuning with elastic beams

The general principles and realizations of FBG wavelength tuning with elastic beams are proposed and demonstrated.Theories and experiments show that when displacement at the center point of simple beams,deflection of cantilever beams and torsion strain of torsion beams are relatively small,Bragg wavelength shifts of sensing FBGs have linear relationship with applied external stress,lateral displacement,torque and torsional angles,respectively.The experimental results indicate that the curvature sensitivity of the simple beam is 1.65 nm/m-1,the displacement sensitivity of the equivalent-strain cantilever beam is 4.4 cm/kg and the torque and torsional angle sensitivities of the torsion beam are 6.27 nm/Nm and 0.086 7 nm/degree,respectively.

High-sensitivity temperature sensor based on long-period fiber grating

Temperature sensitivity is greatly improved by taking the following three measures: proper long-period fiber grating (LPFG) whose strain coefficient of the core is larger than that of the cladding is employed, the LPFG is coated with a thin film of the material whose refractive index decreases with the temperature, and the sensor is encapsulated by metal material whose thermal expansion coefficient is large. By computer simulation, a measured temperature coefficient of 0.2375 nm/oC and a temperature resolution less than 0.1 oC are obtained.