共查询到20条相似文献,搜索用时 15 毫秒
1.
Sugden K. Zhang L. Williams J.A.R. Fallon R.W. Everall L.A. Chisholm K.E. Bennion I. 《Lightwave Technology, Journal of》1997,15(8):1424-1432
Practical, low-loss (<2 dB), fiber Bragg grating single-passband transmission filters have been realized with >30 dB out-of-band rejection over ~25 mm spectral widths. The approach adopted is based on the concatenation of two or more tailored broadband chirped gratings fabricated with low short-wavelength loss to maximize the rejection and stopband width in a filter with ~1 nm passband. The effect of thermal aging for similar complex structures is considered in the context of three different fiber types: standard telecommunication, high germania (Ge)-doped and boron/germania (B/Ge)-codoped. It is shown that while hydrogenated B/Ge-codoped fiber exhibits excellent photosensitivity, the resulting decrease in guiding strength and thermal stability may make germania-doped fiber the more attractive choice 相似文献
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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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基于级联光纤环微波光子滤波器的微波倍频技术 总被引:2,自引:1,他引:1
为了得到高倍频的微波信号,实现获得了一种基于 外调制技术与级联光纤环微波光 子滤波器(FRMPF,fiber ring microwave photonic filters)的新型倍频微波信号光学产生 技术。利用外调制的方法,采用大功率信号驱动马赫曾德尔 调制器(MZM)得到了高阶谐波信号,再利用级联的FRMPF进行选频。理论计算与实验测试了FR MPF的滤波特性。通过调节每个FRMPF的环长,利用第1个FRMPF将基频信号与三阶谐波滤除 ,再通过第2个FRMPF将二阶谐波滤除,最终得到四倍频信号。 研究结果表明,利用频率为2.018GHz 的信号驱动MZM, 得到了 频率为8.073GHz的四倍频信号,信噪比(SNR)大于13dB。 相似文献
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Based on time-space duality, we deduce a time-domain equivalent to the Fraunhofer (far-field) approximation in the problem of spatial diffraction. We can use this equivalence to carry out a real-time optical spectrum analysis, which is shown to be realizable by using, as the dispersive media, filtering devices based on chirped distributed resonant coupling. In particular, we present the design of linearly chirped fiber gratings (reflection configurations) and linearly chirped intermodal couplers (transmission configurations) to work as real-time spectrum analyzers. The proposed systems are shown to work properly by means of simulation tools. Furthermore, we use joint time-frequency signal representations to get a better understanding of the physical processes that determine the behavior of these systems. In this way, we demonstrate that the propagation of a given signal through a chirped fiber grating (or a chirped intermodal coupler), under the temporal Fraunhofer conditions, translates into a temporal separation of the spectral components of the signal. The results of our study indicate potential important applications based on this effect 相似文献
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A wide-band microwave photonic phase and frequency shifter 总被引:1,自引:0,他引:1
Advanced radar deception systems require wide-band devices which perform microwave processing of frequency and phase information. A wide-band microwave photonic phase shifter was constructed which is capable of imposing greater than 2π phase shift to microwave signals in the 2-18-GHz frequency range. The maximum standard deviation from the phase setting was 10° (7° typical). The phase shifter was then incorporated into a frequency translation architecture. The carrier suppression obtained was 50 dB with a spurious harmonic suppression of 23 dB 相似文献
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High-performance all-fiber Fabry-Perot filters with superimposed chirped Bragg gratings 总被引:1,自引:0,他引:1
The performance of large-band Fabry-Perot (FP) filters is investigated through numerical simulations and experimental realization. The limitations of the filters are studied theoretically to determine the impact of the chirped fiber Bragg grating (FBG) imperfections on spectral variations of the free spectral range (FSR), finesse, transmission loss, and polarization dependent loss (PDL). All-fiber FP devices are realized experimentally with finesse reaching 240 and covering a spectral band of 26 nm. For finesse up to 80, the filters present acceptable performance in terms of spectral variations of FSR (/spl plusmn/3%), finesse, attenuation (/spl plusmn/0.5 dB), PDL (<0.2 dB), and insertion loss (<3 dB). 相似文献
10.
Continuously tunable photonic microwave true-time delay based on tunable chirped fibre Bragg grating
A simple scheme for the photonic microwave true-time delay with high tunability based on a tunable chirped fibre Bragg grating without centre wavelength shift is experimentally demonstrated. A large dynamic range of true-time delay from 20 to 200 ps was achieved for a microwave signal carried over an optical signal. 相似文献
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基于啁啾光纤光栅色散补偿问题的思考 总被引:1,自引:0,他引:1
色散已成为光纤长距离、高速率通信中的巨大障碍.鉴于色散补偿光纤插入损耗大、易引入非线性效应等缺点,文章采用啁啾光纤光栅对系统进行色散补偿,克服了以上不足.通过分析啁啾光纤光栅色散补偿的原理,结合理论分析,提出在多通道波分复用系统中使用啁啾光纤光栅,以实现长距离无中继传输. 相似文献
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详细研究了光子晶体光纤长周期光栅(LPG-PCF)的应力和温度特性,利用成功制作的温度不敏感PCF-LPG,实现了两种结构简单光纤传感器.在温度不敏感应力传感器中,PCF-LPG作为温度不敏感的应力传感头,当以波长为1553nm的分布反馈(DFB)激光器为入射光源、用分辨率为0.001dB的光功率计测量时,PCF-LP... 相似文献
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The switchable dual-wavelength erbium-doped fiber laser(EDFL) with a two-mode photonic crystal fiber(PCF) loop mirror and a chirped fiber Bragg grating(CFBG) at room temperature is proposed and experimentally demonstrated.The two-mode PCF loop mirror is formed by inserting a piece of two-mode PCF into a Sagnac loop mirror,with the air-holes of the PCF intentionally collapsing at the splices.By adjusting the state of the polarization controller(PC) appropriately,the laser can be switched between ... 相似文献
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A new type of tunable filter based on a commandable defect in the bandgap of a periodic CPW structure is proposed. The defect level is tuned either mechanically by adding a covering slab over the device or electrically by polarising diodes located at the defect. The validity of this concept is experimentally demonstrated at 4 GHz. This kind of filter is well suited for applications in the 10 to 60 GHz frequency range. 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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The dispersion characteristics of apodized, linearly chirped fiber Bragg gratings and their potential as dispersion compensators have been studied systematically. It is shown that the positive hyperbolic-tangent profile results in an overall superior performance, as it provides highly linearized time-delay characteristics with minimum reduction in the linear dispersion. To compensate for the linear dispersion of 100 km of standard telecom fiber over certain bandwidth (in nanometers), the required grating length is 19.24 cm/nm 相似文献
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Long-period fiber gratings as band-rejection filters 总被引:23,自引:0,他引:23
Vengsarkar A.M. Lemaire P.J. Judkins J.B. Bhatia V. Erdogan T. Sipe J.E. 《Lightwave Technology, Journal of》1996,14(1):58-65
We present a new class of long-period fiber gratings that can be used as in-fiber, low-loss, band-rejection filters. Photoinduced periodic structures written in the core of standard communication-grade fibers couple light from the fundamental guided mode to forward propagating cladding modes and act as spectrally selective loss elements with insertion losses act as backreflections <-80 dB, polarization-mode-dispersions <0.01 ps and polarization-dependent-losses <0.02 dB 相似文献
18.
The properties of the linear chirped fiber grating (CFG) which is used in the true time delay unit of the optical beamforming networks (OBFNs) are studied intensively through theoretical analyses and numerical calculations. It is concluded that the dispersion of the CFG is equal to 1/(3Gc), where G is the chirp coefficient of CFG and c is the light speed. Based on this relationship, a simplified designing process of a CFG which satisfies the requirements of the OBFN is given. The simulation results are coincident with the theoretical conclusions. 相似文献
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《Lightwave Technology, Journal of》1996,14(11):2581-2588
We investigate and compare the equalization performance of various apodization functions in linearly chirped fiber gratings, with a view of determining an optimum profile for the design and fabrication of chromatic dispersion compensators. A discussion concerning the relation of these apodization functions with the group delay characteristic of the equalizer is presented yielding important results connected with the grating design. The analysis has been extended to consider nonideal effects such as nonconstant averaged index and a realistic optical source 相似文献