Generation of high-repetition-rate optical pulse using cascaded long-period fibre gratings

The generation of high-repetition-rate optical pulses using cascaded long-period fibre gratings is proposed. The pulse multiplication is realised by exploiting the difference in the propagation constant of the core and a cladding mode in a standard singlemode fibre. Two, four and eight times pulse multiplication have been successfully implemented with a minimum repetition period of 2.4 ps.     

Generation of a 100-GHz optical pulse train by pulse repetition-rate multiplication using superimposed fiber Bragg gratings

We demonstrate the use of superimposed fiber Bragg gratings (FBGs) operating in reflection as amplitude and phase filtering stages for multiplying the repetition rate of a given optical pulse sequence. In particular, we use a 1-cm-long structure of two superimposed linearly chirped FBGs to generate a continuous optical pulse train with a repetition rate of 100 GHz (duty cycle /spl ap/50%) at a wavelength of 1.55 /spl mu/m from a 10-GHz mode-locked fiber laser.     

光纤延迟线编解码器的设计

光纤延迟线编码解器作为光码分多址系统时域编解码的基本器件,它起的作用是对光脉冲进行延时编码,同时也会给系统带来别的问题。例如：功率分离,延时损耗,温度抖动等。本文介绍了编码器的设计,同时对以上问题进行了分析,得出的结论包括：设计时必须考虑温度的影响,系统的损耗随着码重和用户数的增加而增加。这些可以对系统的设计提供一个参考。     

Compact high frequency true-time-delay beamformer using bidirectional reflectance of the fiber gratings

A compact high frequency true time delay (TTD) beamformer using bidirectional reflectance of the fiber gratings (FGs) is proposed. The FGs can be a set of fiber Bragg gratings (FBGs) or chirped fiber gratings (CFGs). The number and the length of the time delay lines are greatly reduced compared to the previous systems. A phase array antennas system using this TTD beamformer has many advantages including being compact, low requirement on the bandwidth of the tunable laser source and working at high microwave frequency. The proof-of-concept experiment results demonstrated the feasibility of the proposed scheme.     

高频CO2激光脉冲写入的新型长周期光纤光栅及其在光通信中的应用

报道了一种利用频率为几千赫兹的高频CO2激光脉冲的热冲击效应制作长周期光纤光栅的新技术。实验中，作者首次发现这种新型的长周期光纤光栅具有一些独特的光学特性，比如弯曲特性和横向负载特性等，这主要是因为用高频CO2激光脉冲写成的长周期光纤光栅的横截面折射率分布不对称所致。基于这种新型长周期光纤光栅，设计了一种用于减小掺铒光纤放大器噪声系数的ASE噪声滤波器和平坦掺铒光纤放大器增益谱的增益均衡器，此外，还利用这种新型长周期光纤光栅独特的弯曲和压力特性，研究设计了两种用于动态平坦掺铒光纤放大器增益谱的动态增益均衡器。     

在光纤拼接处刻写长周期光纤光栅及其传感应用

在"单模光纤-细芯光纤"拼接处刻写了 Type Ⅱ 型长周期光纤光栅,构成一种高温光纤传感器.该传感器实际由2 段不同的长周期光纤光栅级联构成,在第二个光栅形成了 Mach-Zehnder 干涉,因此,传感器透射谱由长周期光纤光栅与Mach-Zehnder 干涉仪共同作用形成.利用传感器的透射谱与环境温度的线性变化关系...     

Effects of cladding radius on the optical characteristics of long-period fiber gratings

Using three-layer vector field model,the dispersion characteristics and spectral response of long-period fiber gratings（LPFGs）with different cladding radii are analyzed.Both the numerical and experimental results demonstrate that LPFG＇s resonant wavelengths shift towards much longer wavelength and the transmission depth is strengthened significantly by decreasing cladding radius.When the cladding radius is less than 20μm,only a single resonant peak over a wavelength range of 600 nm（from 1200 nm to 1800 nm）is achieved,and the sensitivity of LPFG to external refractive index is enhanced significantly.     

带光纤光栅的MZI型全功能光分插复用器的研究(本期优秀论文)

提出了一种结合光纤Bragg光栅(FBG)和级联马赫-曾德尔干涉仪(MZI)的全功能光分插复用器(OADM).应用扭转梁对光栅对的中心波长实施同步调谐,使两级MZI单元的反射波长错位或动态一致,实现全通和动态上/下路功能.在0.8nm波长间隔、8波长的波分复用系统中,对其输出响应进行了数值模拟,并分析了两光栅相对位置差和两干涉臂长差对响应波形及隔离度的影响.     

梯状光纤延迟线编解码器的设计与实现

梯状光纤延迟线编解码器是各类延迟线编解码器中最有前途的一种。文章就其设计方法进行了详细的分析和讨论，并着重分析了其中光纤耦合器的最佳耦合因子的设计。将不同情况下的耦合因子对自相关峰值和旁瓣抑制比的影响作了比较。研究表明，要实现正确的解码，各点的最佳耦合因子应使旁瓣抑制比和自相关峰值达到最大。据此设计的编解码器具有良好的性能。     

Multiplication and reshaping of high-repetition-rate optical pulse trains using highly dispersive fiber Bragg gratings

A novel technique for simultaneous pulse reshaping and repetition-rate multiplication of mode-locked laser pulse trains using linearly chirped apodized fiber Bragg gratings is proposed. Simple analytical expressions for apodization and phase profiles of the grating are derived. The practical feasibility of this technique is discussed in detail for the case of high-repetition-rate square pulse generation and multiplication.     

应用子结构分析方法计算分析光纤光栅组级联特性

本文介绍了基于矩阵数据库条件下互联网子结构分析方法，并应用该方法对光纤光栅组进行级联特性分析。本文可为实际应用合理选择光栅组织方式及算法提供理论依据。     

Synthesis of long-period fiber gratings with the inverted erbium gain spectrum using the multiport lattice filter model

This paper proposes an accurate modeling technique of concatenated long-period fiber gratings (LPFGs). The proposed technique is then applied to the synthesis of LPFGs for the erbium gain equalization using both the simulated annealing and the steepest descent minimization technique. A piecewise-uniform LPFG is theoretically synthesized according to the inverted gain spectrum of a commercially available erbium-doped fiber amplifier (EDFA) over the range of 1525-1570 nm. Sensitivity analysis of the designed structure is presented by Monte Carlo simulation with regard to the manufactured amplitude mask. To verify a synthesizing technique using the proposed modeling, the piecewise-uniform LPFGs for gain flattening of EDFA are fabricated and their spectra are also presented experimentally.     

Characterization of a full encoder/decoder in the AWG configuration for code-based photonic Routers-part II: experiments and applications

A 200-gigachip/s multiple encoder/decoder in an arrayed waveguide configuration, which generates and recognizes simultaneously 16 optical labels in parallel, has been fabricated. The device has been experimentally characterized, and a 10-Gb/s 50-km optical packet switching (OPS) experiment has been successfully performed: Optical packets are switched to their own destinations using a single device with a processing rate of 13 gigapackets/s.     

Highly stable optical add/drop multiplexer using polarization beam splitters and fiber Bragg gratings

We demonstrate a novel wavelength-division add/drop multiplexer employing fiber Bragg gratings and polarization beam splitters. The multiplexer is easy to fabricate without any special technique such as UV trimming, and yet shows very stable performance with less than 0.3-dB crosstalk power penalty in a 0.8-nm-spaced, 2.5-Gb/s-per-channel wavelength-division multiplexing (WDM) transmission system.     

Generation of synchronized subterahertz optical pulse trains byrepetition-frequency multiplication of a subharmonic synchronousmode-locked semiconductor laser diode using fiber dispersion

We describe the generation of a synchronized, low-jitter, subterahertz optical pulse train by repetition-frequency multiplication of a subharmonic synchronous mode-locked semiconductor laser diode using the group-velocity dispersion (GVD) of optical fiber. A 49-196 GHz optical pulse train was generated with low intensity fluctuation and with low timing jitter, by adjusting fiber length in accordance with the mode-locking frequency and the fiber's GVD     

Interrogation of wavelength multiplexed fiber Bragg gratings using spectral filtering and amplitude-to-phase optical conversion

A technique for interrogating multiplexed FBG sensors using all-fiber low-cost devices is demonstrated. It is based on spectral filtering employing a fused biconical wavelength-division multiplexer and on amplitude-to-phase optical conversion to perform power referencing. Four FBG sensors are wavelength multiplexed in the network, and a 3-nm-wide tunable optical filter is employed at the detection block for sensor demultiplexing. With this technique an operation range of more than 2 nm is demonstrated for the sensors with achievable wavelength static resolution ranging from 1.9 to 13.4 pm/Hz/sup 1/2/ with no observable hysteresis. As for power referencing, the system is proven to be unaffected by power variations as high as 75% of the total power launched by the source. Finally, output-phase variations due to crosstalk are shown to be under 1% of the total output phase range, with more than 29-dB optical isolation between channels.     

利用激光边带注入法实现光脉冲的减速和存储

基于激光边带注入法在铷原子蒸气中实现了电磁诱导透明、光脉冲的减速和存储.为实现对铷原子的相干操控,将主激光器的输出锁定在铷87原子D1线F=1→F'=2的跃迁谱线上,经6.8 GHz电光调制器(EOM)调制后,负一阶频率边带与D1线F=2→F'=2跃迁频率共振.将负一阶频率边带注入锁定从激光器,主激光器和从激光器输出的两束激光和铷原子的两基态超精细能级达到双光子共振,实现相干操控铷原子.将主激光器和从激光器输出的两束激光作为探测光和耦合光输入到铷泡中,通过操控两光束的波形和开关观察到电磁诱导透明、光脉冲的减速和存储.     

双极性和单极性编解码的性能比较

介绍了采用光正交码与素数码的单极性光延迟编解码器和采用光延迟平衡与非平衡结构的双极性编解码OCDMA系统,并对它们的性能进行了比较.结果表明,双极性编解码比单极性编解码的误码率有几个数量级的改善,用户数可提高近10倍.     

Wavelength conversion of SCM signals using semiconductor optical amplifiers: theory, experiments, and applications

In this paper, we deal with the subject of cross-gain modulation (XGM) and cross-phase modulation (XPM) semiconductor optical amplifier-based wavelength conversion of optical channels carrying subcarrier multiplexing signals in a comprehensive way. The equations and models that describe the conversion process and the resulting harmonic and intermodulation distortions are obtained showing the superior performance of XPM over XGM in terms of secondand third-order distortion and contrast ratio. Experimental results for XGM-based wavelength conversion that confirm the results predicted by our theoretical models are presented, and finally, we consider the specific application of wavelength conversion of optical channels carrying full frequency plans such as that of cable television applications.