Dispersion compensation by optical phase conjugation in silicon waveguide

The use of a silicon-waveguide-based optical phase conjugator at the mid-span of a fibre link for dispersion compensation is experimentally demonstrated, enabling transmission of optical data at up to 40 Gbit/s over 320 km of standard fibre with clear open eye diagrams at the receiver. In addition, the feasibility of dispersion compensation for multiple DWDM channels simultaneously is demostrated. A signal conversion efficiency of -10 dB is obtained with a pump intensity of 37.5 MW/cm² in the waveguide.     

相位共轭镜变换矩阵及相位共轭光腔

本文提出了能更确切地描述相位共轭镜运转特性及揭示相位共轭镜工作本质的变换矩阵。将新矩阵用于研究相应的相位共轭光腔，分别讨论了从RM和PCM端输出的简并模和非简并模。     

光折变相位共轭技术的研究进展

简要地介绍了光折变相位共轭技术的研究概况,着重介绍了自泵浦相位共轭镜及互泵浦相位共轭镜的研究进展,对它们的结构及机理做出了说明。     

补偿色散和非线性相位噪声的新型光谱反演器

设计了一种新型光谱反演器,并演示了该器件在光纤传输系统中对于色散和非线性相位噪声的补偿作用。该补偿作用可以使得光纤传输系统的有效传输距离得到显著的提高,对于未来光传输系统的发展有着重大的作用。     

Techniques for nonlinearity cancellation into embedded links by optical phase conjugation

One of the main causes of signal degradation in high-bit-rate transmission systems is the interplay between fiber nonlinear effects and dispersion. Different techniques to compensate nonlinear effects in transmission systems, by using an optical phase conjugator, have been proposed in the literature. In this paper, two different innovative setups allowing nonlinearity cancellation in an embedded link are disclosed. The proposed schemes are simpler than those previously described and strongly improve systems performances. The physical mechanism allowing nonlinearity compensation is depicted, and the effectiveness of the proposed solutions is numerically demonstrated. Moreover a new practical method, useful for performance optimization of systems including a phase conjugator, is presented. Results apply to any bit-rate and modulation format.     

采用简单泵浦相位共轭镜实现的光学关联存储器

本文设计了一种结构简单的相位共轭镜,并用KNSBN:Ce光折变晶体作为存储介质和相位共轭镜实现了光学关联存储。文中给出了有关的实验结果。     

Noise characteristics of fiber-based optical phase conjugators

This paper presents a theoretical and experimental analysis of the noise characteristics of a fiber based optical phase conjugator. The results are used to derive an expression for the noise figure (NF) of the device. The lowest measured NF is 18 dB, at -15 dB net conversion efficiency. This NF was limited by stimulated Brillouin scattering (SBS) and amplified spontaneous emission from an optical amplifier. Using the experimental parameters, the theoretical values agree well with the measurements, and predicts in our particular case a minimum NF of 10 dB at high conversion efficiencies. Furthermore, we investigate the influence of optical amplifiers before and after the conjugator, and, with all excess noise eliminated, we predict the quantum limit of 3 dB at efficiencies much greater than 100%     

Theory of photorefractive phase conjugators with mutuallyincoherent beams

Plane-wave analysis of the recently demonstrated photorefractive phase conjugators with mutually incoherent beams is presented. Based on four-wave mixing theory, two important configurations, the bird-wing phase conjugator and the mutually incoherent beam coupler are investigated by solving coupled nonlinear equations with beam depletion and absorption. Various intensity performances are theoretically analyzed. Different configurations of this kind of mutually incoherent phase conjugators are compared. Competition of different processes is discussed. Experimental data are well fitted by the theory     

Experimental demonstration of nonlinearity and dispersion compensation in an embedded link by optical phase conjugation

We report in this letter, the experimental demonstration of simultaneous dispersion and nonlinearity compensation in an embedded link characterized by strongly asymmetrical power profiles. This result is obtained by using a highly efficient optical phase conjugator based on a periodically poled lithium-niobate waveguide, combined with two small dispersion-compensating elements properly inserted in the link.     

Pulse evolution in a photorefractive self-pumped phase conjugatorwith transmission grating geometry

The effect of grating dispersion on pulse evolution in a photorefractive self-pumped phase conjugator is analyzed. The broadening factors and the time-dependent phases of self-pumped phase-conjugate pulses of unchirped and chirped Gaussian pulses are obtained. When the grating dispersion and the angular dispersion cancel the material dispersion, the self-pumped phase-conjugate pulse has a minimum width, which is determined by the first-order dispersion of the grating. The self-pumped phase conjugation of an unchirped Gaussian pulse broadens and is linearly chirped whereas the self-pumped phase conjugation of a chirped Gaussian pulse is compressed when the dispersion-induced chirp cancels the initial chirp     

相位共轭反馈He—Ne激光器的噪声特性

本文报导了相位共轭反馈He－Ne激光器的噪声特性，观测到激光起伏存在两种变化过程，即几十赫兹的快变过程和秒量级的慢变过程，在远离半腔长整数倍处，相位共轭反馈只影响其激光器本征噪声的周期性，其噪声幅度变化较小，在一倍腔长处，噪声起伏约为激光输出的35％．     

Suppression of Gordon-haus effect and interaction of dark soliton by optical phase conjugation

The optical phase conjugation is put forward for the first time to suppress the Gordon-Haus effect caused by amplifier spontaneous emission noise, and soliton interaction in the dark soliton transmission system. The simulation results show : If the conjugator is sited at proper situation, it can suppress the Gordon-Haus effect or the dark soliton interaction effectively.     

非相干光对光折变相位共轭镜的非负效应

本文以BaTiO3:Ce自汞浦相位共轭镜为例,理论上和实验上对非相干光作用在光折变相位共轭镜的四波混频区产生的非负效应进行探讨和验证。     

Phase conjugator for active retrodirective array applications

A novel phase conjugator for active retrodirective array applications is presented. The circuit provides conversion gain as well as phase conjugating operation by using active devices, and results in a simple and compact design through the use of a common port for RF and IF signals. Measurement results indicate a 3.2 dB conversion gain with an RF-IF isolation of 20 dB. This phase conjugator can be used as a component in a retrodirective array when combined with an antenna     

Optimization of DSF- and SOA-based phase conjugators byincorporating noise-suppressing fiber gratings

We compare the performance of dispersion-shifted-fiber (DSF) and semiconductor-optical-amplifier (SOA) based laser phase conjugators for a 10-Gb/s nonreturn-to-zero system with respect to conversion efficiency, noise figure, and distortion. Fiber gratings are used for signal extraction and amplified spontaneous emission (ASE) suppression, allowing closer wavelength spacing and reducing the conjugation noise figure by up to 12 dB. Despite the higher SOA conversion efficiency, both conjugators give similar noise figures with ASE suppression. However, the DSF-based conjugator has the advantage of distortion tolerance at higher input power     

熔石英棒和光纤构成的新型复合型相位共轭镜

提出一种使用熔石英棒和光纤构成的新型复合型相位共轭装置,并在实验中得以实现.这种组合将具有高的激光损伤阈值的大直径熔石英棒和具有较低的受激布里渊散射(SBS)阈值的光纤结合在一起,构成了振荡-放大形式的双池式受激布里渊散射结构,使得从光纤受激布里渊散射反射的斯托克斯光注入到熔石英介质中形成了强迫受激布里渊散射过程.在这种机制下,该复合型相位共轭镜较之单块熔石英棒、单根光纤或组合芯径光纤这三种形式的相位共轭镜,具有更低的受激布里渊散射阈值和更高的受激布里渊散射反射率,而且可以在较高的输入功率下运行.实验中将其用于高重复频率高功率的激光二极管(LD)抽运激光主振荡放大(MOPA)系统中,在100 Hz重复频率下获得了42.05%的反射率,并且获得了很好的光束质量,光束质量因子M2值从输入光束的3减少到1.6,反射光斑稳定.在400 Hz下光束质量因子M2值达到1.7.     

连续钛宝石激光器光折变位相共轭外腔的实验研究

利用Ce：BaTiO3晶体构成的自抽运位相共轭(SPPC)外腔，改善了连续钛宝石激光器的工作特性，使得激光输出阈值由未加位相共轭腔时的4．7W下降到加位相共轭腔时的3．6W，斜率效率由26％上升为30％。利用外腔激光理论对该实验结果进行了合理的分析。此外，由于位相共轭自扫描效应，导致了输出光中心频率在反馈后3min时蓝移了142MHz，在6min时红移了243MHz。通过直接测量暗条件下自抽运位相共轭反射率的衰减，得到了自抽运位相共轭光栅的暗存储特性。在暗条件下，位相共轭反射率在开始的1．5h内由80．5％下降到75％，随后缓慢下降，到17h位相共轭反射率仍保持在74％。     

BaTiO_3∶Ce桥式互泵浦相位共轭镜的研究

本文首次用两台He-Ne激光器在光折变晶体BaTiO3：Ce中实现了桥式工系浦位共轭，并实验确定了工系渝光的最佳人射角度。对BaTiO3:Ce桥式互泵辅相位共轭镜的形成机理作了分析，并对实验的结果和现象进行了讨论．     

Nonlinear response of the photorefractive phase conjugator: aperturbation analysis

Using perturbation theory, an examination is made of the fidelity of the photorefractive degenerate four-wave mixing phase conjugator. The general case is considered in which the probe is spatially varying (a beam) and temporally varying (a pulse), and the pumps are allowed to deplete. The probe wave is expanded as a sum of monochromatic plane-wave components. Carrying out the perturbation procedure up to the third order, the authors found that the components of the probe interact in pairs, so that the reflectance of each component of the conjugate wave is a combination of a linear term, a self-nonlinear term, and a term representing crosstalk with all other components of the probe. The crosstalk effect as a function of the frequency difference exhibits resonance behavior     

Optical-fibre phase modulator

A clip-on piezoelectric transducer is described which may be easily attached to a plastics-coated optical fibre and used to phase modulate signals within the glass fibre. The technique is applicable to a 1-way optical telemetry highway.