共查询到20条相似文献,搜索用时 15 毫秒
1.
LIU Yu-yong FU Hong-yan 《光电子快报》2007,3(6):413-416
A general theoretical model for microwave photonic filters based on multi-wavelength light source and dispersive media is summarized and presented, and is applied to the analysis of double-laser-based microwave photonic notch filters’ performance. The different influences of the double-sideband(DSB) modulation and the single-sideband(SSB) modulation are demon- strated and explained theoretically. Furthermore, the impact of different factors, such as frequency spacing, 3dB bandwidth and the spectrum amplitude mismatch on the performance of the microwave photonic notch filters are also studied. The numerical simulation results are in good agreement with predictions, and could be beneficial for future optimization of microwave photonic filters. 相似文献
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Diffraction efficiency of grating plays an important role in output power of incoherent fiber laser beam combination. Through theoretic analysis and numerical simulations it has been proved that the diffraction efficiency would increase with the decrease of grating frequency and wavelength bandwidth. On the condition that the width of a fiber array is fixed at W=10 cm, an optimum grating frequency were numerically simulated as f=230 mm-1. Also an unequal interval method was proposed to improve the system efficiency of diffraction into 0.4293, which is higher than 0.3824 under the equal interval condition. 相似文献
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SHENLu-fa WANGZi-hua 《光电子快报》2007,3(4):257-259
In the weakly guided case, the power propagation in the core and the cladding of a left-handed material fiber is obtained by solving Maxwell’s equations. The wave-guide efficiency is analyzed at cutoff and far from cutoff. Far from cutoff, the wave-guide efficiency equals to 1. At cutoff, for m=0, 1, the wave-guide efficiency equals to zero; for m=2, the wave-guide efficiency approaches to infinite; for m>2, the wave-guide efficiency is less than zero, but its absolute value is larger than 1. Those are novel characteristics of left-handed material fiber. 相似文献
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FU Hong-yan OU Hai-yan CHEN Da-ru XIAO Yun HE Sai-ling 《光电子快报》2007,3(6):406-409
The tunable microwave photonic filter based on a fiber ring and erbium-doped fiber amplifier (EDFA) was proposed. By introducing a section of erbium-doped fiber (EDF) into the fiber ring, the loss of the signal can be compensated by the EDFA gain through adjusting the pump power. This can largely increase the number of the effective sampling taps, and then improve the performance of the microwave photonic filter notably. When the pump power was set to be 42.7 roW, a microwave bandpass filter with the 3-dB bandwidth of 0.15 MHz, the Q factor up to 100 and extinction ratio up to 20 dB was achieved. By employing a tunable optical delay line in the above fiber ring, a tunable microwave photonic filter has been realized through tuning the length of the optical delay line. The proposed tunable microwave photonic filter can fred great applications in microwave signal processing and ROF system. 相似文献
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V.Striano V.Latini G.Coppola LRendina 《光电子快报》2007,3(4):260-263
This paper describes our research activity involved in the identification, development and test of a prototype SHM system constituted by optical sensing nodes to measure both temperature and strain on ultra high temperature ceramics (UHTC) materials up to 1000 °C. Commercially available optic devices can operate up to 550 °C. To raise temperature limit up to 1000 °C, custom devices, mainly under development for scientific applications, have been identified. A prototype SHM system has been developed adopting a FBG sensor for temperature measurement and an EFPI sensor in sapphire fiber for strain measurement. The preliminary findings from thermo-mechanical tests indicate that former SHM system is capable of accurately measuring strain at elevated temperatures on UHTC materials. 相似文献
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KANG Yun YE Cheng-chun LUO Zheng-qian SI Miao-ling 《光电子快报》2007,3(2):112-114
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. 相似文献
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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. 相似文献
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HAN Gui-hua ZHANG Wei-gang 《光电子快报》2007,3(3):195-198
A novel method of correlation function for analyzing cross-sensitivity between strain and temperature is reported for the first time in this paper. Using the new method,the correlative characteristics between strain and temperature of fiber Bragg grating sensors are studied both theoretically and experimentally The experimental results accord with the theoretical calculations. 相似文献
10.
GU Zheng-tian Xu Yan-ping DENG Chuan-lu 《光电子快报》2008,4(2):106-109
Based on the dual peak resonance of long-period fiber grating(LPFG), a novel film sensor is presented, in which films sensitive to the surrounding gases are coated on the cladding of the fiber grating region, and the intervals of the dual peak resonant wavelengths change with the film refractive index. According to the coupled-mode theory, a triple-clad numerical model is developed to analyze the relation between the sensitivity Sn and the thin film optical parameters (the film thickness h3 and the refractive index n3) and the fiber grating parameters (the grating period A and the core index modulation σ). By using optimization method, the optimal film optical parameters and the grating structure parameters are obtained. Numerical simulation shows that the sensitivity of this scheme to refractive index of the films is predicted to be more than 10-7. The theoretic analysis provides straightforward foundation for the actual highly sensitive film sensors. 相似文献
11.
An optical sensing system for the concentration of methane based on fiber Bragg gratings 总被引:1,自引:0,他引:1
ZHOU Bin LIU Guo-rong GUAN Zu-guang HE Sai-ling 《光电子快报》2007,3(6):410-412
Based on a special catalyst and fiber Bragg gratings (FBGs), an optical sensing system is proposed to measure the concen- tration of methane. The temperature of the catalyst rises rapidly as the concentration of methane increases, and hence it can be detected by an FBG-type sensor through monitoring the wavelength shift of the reflection spectrum. The experimental results show the good performances of our system, such as the high resolution and temperature stability. 相似文献
12.
GUO Xuan LIU Feng BI Wei-hong 《光电子快报》2007,3(3):199-202
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. 相似文献
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CHU Xing-chun ZHAN Sheng-bao ZHAO Shang-hong LI Yun-xia XU Jie 《光电子快报》2007,3(6):455-458
A novel method for phase-detecting of each individual beam in coherent beam combining system of fiber laser array based on the property of time-shift of fast Fourier transform is reported. It takes advantage of the relative movement of fringe- pattern to detect the phase shift between each individual beam and reference beam. No frequency shift component for reference beam is required in the system. At the same time, the acquisition fringe-pattern is firstly tailored to a few multiple of fringes in order to reduce the phase-detecting error caused by energy leakage during the course of fast Fourier transform. This technique can greatly reduce the effect of energy leakage and thus improve the phase-detecting precision. Basic principle of the new phase-detecting method is described in detail, and numerical results show that the phase-detecting error is less than 1/1000 wavelength by utilizing our method. 相似文献
14.
A new type of high-power broadband superfluorescent source of Yb^3+ -doped double-cladding photonic crystal fiber is reported experimentally, which is pumped at 976 nm by a high-power laser diode with the end-coupling method. We have obtained a smooth broadband output of superfluorescence The maximum output power is 1.649 W with a slope efficiency of 56.7%. The 3 dB bandwidth is 22.4 nm To the best of our knowledge, this is the first report about SFS with such high output power of 1.649 W. 相似文献
15.
ZHANG Hui CHANG Sheng-jiang ZHANG Yan-xin ZHAO Xiang-ting 《光电子快报》2008,4(2):103-105
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. 相似文献
16.
V型槽侧面耦合是目前双包层光纤泵浦光耦合的方法之一.本文提出了一种新的制作V型槽进行侧面泵浦的工艺方法,即在光纤预制棒上进行刻槽,然后对侧面已刻出一长条V型槽的顶制棒进行拉丝.针对这种新的侧面泵浦方法的耦合效率进行了理论的分析和计算.通过对交迭场的积分求出这种新的侧面泵浦方法的耦合效率,并对激光二极管阵列距离V型槽的位置以及V型槽所开的角度进行了优化.为随后的实验提供了理论依据. 相似文献
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In recent years ,the demand of the project survey grewincreasingly,sothetorsionsensor has obtainedextensiveattention.But the related studies about optical fiber tor-sionsensor are veryfewinthe domestic andforeign[1-3].Inthe traditional torsion sensor we p… 相似文献
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Design optimization for efficient erbium-doped fiber amplifiers 总被引:3,自引:0,他引:3
The gain and pumping efficiency of aluminosilicate erbium-doped fiber amplifiers (EDFAs) are analyzed as a function of guiding parameters and Er-doping profile for two pump wavelengths of λ p=980 nm and λp=1.47 μm. Three designs of fiber-amplifier waveguides are considered: one with the same mode size as standard 1.5-μm communication fibers (type 1); one with the same mode size as standard 1.5-μm dispersion-shifted fibers (type 2); and one with mode size smaller than those of communication fibers (type 3). For the 1.47-μm pump, fundamental LP01 mode excitation is assumed, while for the λp=980-nm pump, concurrent excitation of LP11 modes is considered. It is shown that excitation of higher-order pump modes at 980 nm does not significantly affect the amplifier gain performance. The effect of concentrating the Er3+ doping near the center of the fiber core is shown to increase the amplifier gain coefficients by a factor of 1.5 to 2 相似文献