光纤光栅群时延纹波对微波光子滤波性能的影响

建立了一种研究光纤光栅群时延纹波(GDR)对微波光子滤波性能影响的理论模型,探讨了群时延纹波对相干光源型和非相干光源型微波光子滤波器性能的影响。基于该理论模型,分别在随机分布的GDR和实测GDR影响下,分析了微波光子滤波器幅频响应、相频响应的演变趋势。相干光源型滤波器中,GDR主要影响体现为陷波点频率的偏移,而非相干光源型滤波器中GDR则导致幅频响应形状和线性相位畸变;而在多抽头情形下,GDR导致边模抑制比下降和消光比劣化。     

光纤光栅群时延纹波对微波光子滤波性能的影响

建立了一种研究光纤光栅群时延纹波(GDR)对微波光子滤波性能影响的理论模型,探讨了群时延纹波对相干光源型和非相干光源型微波光子滤波器性能的影响。基于该理论模型,分别在随机分布的GDR和实测GDR影响下,分析了微波光子滤波器幅频响应、相频响应的演变趋势。相干光源型滤波器中,GDR主要影响体现为陷波点频率的偏移,而非相干光源型滤波器中GDR则导致幅频响应形状和线性相位畸变;而在多抽头情形下,GDR导致边模抑制比下降和消光比劣化。     

Reconfigurable microwave photonic transversal filter using a variable gain tilt filter

A novel and simple technique to realize reconfigurable microwave photonic transversal filter is presented. In the proposed method, a multi-wavelength source and a dispersive medium are applied to achieve multiple taps; and an electro-optic ceramic material-based variable gain tilt filter (VGTF) is utilized to control the tap weights of the filter. The VGTF is computer-controlled via a universal serial bus interface, which enables real-time reconfiguration of the filter. Filter responses with different passband bandwidth and different sidelobe suppression can be achieved. Compared with previous approaches, the given method features in less optical components involved and faster response speed. A three-tap reconfigurable filter with sub-millisecond response speed is experimentally demonstrated.     

Optimization of long-period grating inscribed in large mode area photonic crystal fiber for design of bandstop filter

By inscribing long period grating (LPG) in a photonic crystal fiber (PCF), optical filters for communication wavelengths can be fabricated. In this paper, by utilizing coupled-mode theory and enhanced improved vectorial effective index method, a design of bandstop filter based on optimal LPG parameters is presented where the optimized full-width half-maximum (FWHM), the number (N) and total length of gratings of LPGs (L) are determined. As a result, by the determination of optimized LPG parameters with an optimum length of L_opt=6.5 mm and optimum number of grating N_opt=27 inscribed in the PCF, a bandstop optical filter with FWHM=1 nm is designed.     

多信道梳状滤波器信道间的相移补偿（已撤稿）

采样大啁啾光纤光栅理论（LCSBG）是实现超高信道数梳状滤波器的理想方案,但实际制作时存在信道间隔不准确、多信道无法同时对齐的问题,文中通过对多信道梳状滤波器反射谱特性的数值模拟分析以及信道间隔误差进行了理论计算,指出问题的来源为LCSBG 要求的光栅为周期倒数线性啁啾,并不是简单的线性啁啾.对此,提出了相移补偿方案,并以100信道,40 GHz 梳状滤波器为例进行了仿真验证,得到了理想的结果.这为实际制作高信道、高准确度的多信道梳状滤波器打下了良好的理论基础. 关键词： 光纤光栅 采样大啁啾 相移 多信道梳状滤波器     

磁光光纤光栅滤波器的全光时钟提取性能研究

研究了磁光耦合强度对磁光光纤布喇格光栅中模式转换光反射光谱特性的影响.根据磁光耦合模理论并结合光纤布喇格光栅的传播特性,数值分析了磁光光纤布喇格光栅的磁控特性,得到了3 dB带宽可调的滤波器.采用级联磁光光纤布喇格光栅构造磁控梳状滤波器,实现了40 Gbps归零数据信号的全光时钟提取仿真,分析了时钟信号的抖动性能与磁光耦合参量的关系.     

多信道梳状滤波器信道间的相移补偿

采样大啁啾光纤光栅理论（LCSBG）是实现超高信道数梳状滤波器的理想方案,但实际制作时存在信道间隔不准确、多信道无法同时对齐的问题,文中通过对多信道梳状滤波器反射谱特性的数值模拟分析以及信道间隔误差进行了理论计算,指出问题的来源为LCSBG 要求的光栅为周期倒数线性啁啾,并不是简单的线性啁啾.对此,提出了相移补偿方案,并以100信道,40 GHz 梳状滤波器为例进行了仿真验证,得到了理想的结果.这为实际制作高信道、高准确度的多信道梳状滤波器打下了良好的理论基础.     

磁光光纤光栅滤波器的全光时钟提取性能研究

研究了磁光耦合强度对磁光光纤布喇格光栅中模式转换光反射光谱特性的影响.根据磁光耦合模理论并结合光纤布喇格光栅的传播特性,数值分析了磁光光纤布喇格光栅的磁控特性,得到了3dB带宽可调的滤波器.采用级联磁光光纤布喇格光栅构造磁控梳状滤波器,实现了40Gbps归零数据信号的全光时钟提取仿真,分析了时钟信号的抖动性能与磁光耦合参量的关系.     

Four-wave mixing self-stability based on photonic crystal fiber and its applications on erbium-doped fiber lasers

The analytic solutions of coupled-mode equations of four-wave mixings (FWMs) are achieved by means of the undepleted approximation and the perturbation method. The self-stability mechanism of the FWM processes is theoretically proved and is applicable to design a new kind of triple-wavelength erbium-doped fiber lasers. The proposed fiber lasers with excellent stability and uniformity are demonstrated by using a flat-near-zero-dispersion high-nonlinear photonic-crystal-fiber. The significant excellence is analyzed in theory and is proved in experiment. Our fiber lasers can stably lase three waves with the power ripple of less than 0.4 dB.     

A cheap and practical FBG temperature sensor utilizing a long-period grating in a photonic crystal fiber

A whole temperature sensor in one package utilizing a fiber Bragg grating (FBG) made in a conventional single-mode fiber and which uses a long-period grating (LPG) made in a photonic crystal fiber is proposed and experimentally demonstrated. The function of the interrogation is that the wavelength change of the FBG with environmental temperature is transferred to the intensity of the output via the LPG. Utilizing the temperature-insensitivity of the LPG in the PCF, the interrogation is stable and enables a cheap and practical temperature measurement system with a wide dynamic range.     

Tunable and reconfigurable microwave photonic filter based on cascaded modulation for multi-taps generation

In this paper, a theoretical analysis and experiment to obtain the tunable and reconfigurable microwave photonic filter is proposed. The sidebands generated by cascaded modulation serve as the multi-taps, and then the reconfigurability and tunability can be realized by adjusting the operating condition of intensity modulators and the optical phase shifting between modulators.     

合肥光源横向束流反馈系统中矢量运算单元和光纤陷波滤波器的研制

合肥光源横向束流反馈系统已经建成,着重介绍了系统中矢量运算单元和光纤陷波滤波器的研制。矢量运算单元中使用混频器控制信号的衰减,调节控制电压的大小以控制反馈信号的相位;光纤陷波滤波器创新性地提出用光纤延时制作陷波滤波器,很好地滤除了信号中的回旋频率分量,节省了反馈功率。     

A comparative performance evaluation of micro-Raman spectrograph using holographic notch filter and dielectric filter

An indigenously designed and developed micro-Raman spectrograph, consisting of a diode-pumped solid-state green laser for the excitation of Raman scattering, a Raman imaging microscope, CCD as a detector and a notch filter, has been extensively studied to evaluate its performance. A dielectric edge filter (having 27 alternate layers of SiO₂ and TiO₂) and a holographic notch filter (Oriel make) have been used to block the Rayleigh scattered light from the sample to the entrance slit of the spectrograph. Holographic notch filter is found to be able to record the Raman shifts below 700 cm⁻¹ conveniently whereas dielectric edge filter (27 layers) has enabled the spectrograph to record the Raman spectra very efficiently after a wave-number shift of 700 cm⁻¹. It has also been observed that the instrument using the edge filter provides a peculiar spectrum consisting of three spectral lines having Raman shifts as 569, 1328 and 1393 cm⁻¹ in the Raman spectrum of a weakly scattering sample with large reflectivity. Similarly, a spectrum consisting of multiple lines has been observed when the instrument is being operated using a holographic notch filter. These spectral lines are not observed in the case of liquid samples such as benzene, carbon tetrachloride, ethanol, diethyl ether etc. The origin of these peculiar spectral lines has been briefly discussed in the paper. Additionally, a major motivation for this work is to utilize the results for the selection of an appropriate filter depending on the type of the sample, i.e. weakly scattered and highly reflecting sample or highly scattered and low reflecting sample.     

Proposal and realization for a broadband all-fiber non-uniformly spaced multi-channel optical filter

In this paper, we propose a broadband all-fiber non-uniformly spaced multi-channel optical filter, which is based on the utilization of paired multi-channel fiber Bragg gratings (FBGs) located at two arms of an interferometer. Unlike the traditional optical comb filter, the channel spacing may be either linearly or nonlinearly chirped. Serving as an example, two identical linearly-chirped 51-channel FBGs have been successfully employed to demonstrate the proposed filter experimentally.     

Photonic generation of microwave signals using dual-wavelength single-longitudinal-mode fiber lasers

Photonic generation of microwave signals is demonstrated with a dual-wavelength single-longitudinal-mode erbium-doped fiber ring laser. Microwave signal with a frequency of 21.07 GHz is obtained by aligning the reflection band of a uniform fiber Bragg grating to the two transmission peaks within a fiber Bragg grating-based Fabry-Perot filter. Stable dual-wavelength single-longitudinal-mode operation is guaranteed by means of the combined filtering effect of a saturable absorber and the Fabry-Perot filter. This approach provides an effective solution to the photonic generation of high-frequency microwave signals.     

Performance comparison for RZ-DPSK signal in DCF-based and CFBG-based dispersive transmission system

The impact of the phase noise induced by self-phase modulation and intrachannel nonlinear effect for return-to-zero differential phase-shift keying (RZ-DPSK) in long haul 40 Gb/s transmission systems where dispersion is compensated by chirped fiber Bragg grating (CFBG) is analyzed and numerical evaluated, and it is compared with what is derived from the conventional DCF-based phase-modulated system. Our work also provides a clear physical picture of how the transmission performance is affected by CFBG, which is instructive for further research on CFBG compensated phase-modulated formats.     

Design and analysis of two-dimensional photonic crystals channel filter

A novel three-port channel add/drop filter consisting of two waveguides and two cavities is proposed. One is used for a resonant tunneling-based channel add/drop operation from the bus waveguide to the add/drop waveguide, while the other is used to realize the wavelength-selective reflection feedback in the bus waveguide. By means of coupled mode theory in time, the conditions to achieve 100% add efficiency are derived thoroughly. Based on these theoretical analysis, the channel add filter and some other multi-channel filters are designed in two-dimensional photonic crystals (2D PCs) with square lattice of dielectric rods in air. The numerical results by using the finite-difference time-domain (FDTD) method demonstrate almost complete channel add/drop tunneling at resonance via the three-port systems.     

Theoretical and experimental study of Chen chaotic system with notch filter feedback control

Since the past two decades, the time delay feedback control method has attracted more and more attention in chaos control studies because of its simplicity and efficiency compared with other chaos control schemes. Recently, it has been proposed to suppress low-dimensional chaos with the notch filter feedback control method, which can be implemented in a laser system. In this work, we have analytically determined the controllable conditions for notch filter feedback controlling of Chen chaotic system in terms of the Hopf bifurcation theory. The conditions for notch filter feedback controlled Chen chaoitc system having a stable limit cycle solution are given. Meanwhile, we also analysed the Hopf bifurcation direction, which is very important for parameter settings in notch filter feedback control applications. Finally, we apply the notch filter feedback control methods to the electronic circuit experiments and numerical simulations based on the theoretical analysis. The controlling results of notch filter feedback control method well prove the feasibility and reliability of the theoretical analysis.     

Tunable optical bistability at microwave frequency based on 1D sandwich photonic structure consisting of a nonlinear dielectric slab and two magnetized cold plasma layers

In this paper, tunable optical bistability that denotes the relationship between input intensity and output intensity is numerically investigated in the microwave frequency region based on the one-dimensional (1D) sandwich photonic structure consisting of a Kerr-type nonlinear material slab and two magnetized cold plasma layers. Results show that, in the case of TM-polarized electromagnetic wave, width and switching thresholds of the bistability loops are dependent on the working frequency, initial incidence angle, layer thickness, plasma density, and external magnetic field, which should be judiciously selected to obtain a required bistability behavior. Compared to the case of switch-down threshold, the switch-up threshold in the bistability loop is more sensitive to the changes of parameters. Through this study, the suggested 1D sandwich photonic structure is beneficial to the all-optical signal processing.     

Photonic generation of microwave arbitrary waveforms

In this paper, techniques to generate microwave arbitrary waveforms based on all-fiber solutions are reviewed, with an emphasis on the system architectures based on direct space-to-time pulse shaping, spectral-shaping and wavelength-to-time mapping, temporal pulse shaping, and photonic microwave delay-line filtering. The generation of phase-coded and frequency-chirped microwave waveforms is discussed. The challenges in the implementation of the systems for practical applications are also discussed.