介质化学结构对受激布里渊散射特性的影响

为了研究介质化学结构与受激布里渊散射(SBS)的关系,分析了介质化学结构对极化率、电致伸缩系数、增益系数、声子寿命、布里渊频移、吸收系数和光学击穿阈值等受激布里渊散射特性的影响。讨论了不同介质SBS特性有差异的因素。     

受激布里渊散射(SBS)中的三类介质

介绍了目前使用的三类受激布里渊散射介质的化学结构及其SBS性能．并且分析了受激布里渊散射对介质的要求，     

SBS—FOG中受激布里渊散射光偏振特性的理论分析

本文考虑了双折射效应对保偏光纤两个偏振主轴方向上受激布里渊散射（SBS）光增益的影响,利用Jones矩阵理论分析了受激布里渊散射光纤陀螺（SBS－FOG）敏感环中在保偏光纤熔接点进行角的偏振主轴旋转后受激布里渊散射光的偏振特性,得出当θ=90度时,在敏感环中的受激布里渊散射光不仅具有最大偏振度,而且还使其中的两个本征偏振态（ESOP）达到稳定的结论。θ     

单频保偏掺Yb光纤放大器中的受激布里渊散射实验研究

实验研究了单频单模保偏掺Yb光纤放大器中的受激布里渊散射(SBS)效应。采用前向抽运的两级级联掺Yb光纤放大器,研究了保偏光纤放大器中的受激布里渊散射的光谱变化特性。理论计算的单模光纤的布里渊频移和SBS阈值与实验测试的结果进行了比较。在光纤放大器前后两端观察到多级次的斯托克斯(Stokes)谱线和多级的反斯托克斯(anti-Stokes)谱线,这是由级联受激布里渊散射和四波混频过程产生的。     

单模光纤中受激布里渊散射阈值研究

分析和讨论了受激布里渊散射(SBS)阈值计算的Smith模型和Küng模型,研究了更为准确估算光纤中布里渊散射阈值的方法,通过布里渊增益系数与光纤长度的关系,发现对于较短长度光纤,其布里渊增益系数随着光纤长度变化范围较大,仅在长距离光纤时,布里渊增益系数才可以近似为常数。实验测量了25 km单模光纤的受激布里渊散射阈值,推导出用布里渊时域反射仪(BOTDR)测量受激布里渊散射阈值计算公式,最后用布里渊时域反射仪测量了不同长度光纤受激布里渊散射阈值,实验结果与理论分析吻合。     

基于光纤光栅的微波扫描单边带调制法测量光纤布里渊散射特性

利用光纤布拉格光栅(FBG)和马赫-曾德尔电光调制器实现了单边带光调制输出。基于微波扫描的单边带调制技术提出了一种测量光纤受激布里渊散射(SBS)特性的方法,可有效地将布里渊频移与布里渊增益谱的测量统一起来。对一段50m长的光子晶体光纤(PCF)的SBS特性进行了测量,得到了PCF的SBS谱的布里渊频移为9.7443GHz,布里渊增益谱线宽为22.472MHz,布里渊增益系数为7.874×10-12 m/W。     

液态介质纵向振动对受激布里渊散射反射性能的影响

结合静态流体力学理论、弦振动理论及瞬态受激布里渊散射(SBS)理论,建立了描述介质纵向振动所产生的附加密度变化的受激布里渊散射耦合模型。以四氯化碳为介质,研究了不同强度的基频及倍频振动对受激布里渊散射反射率以及波形失真度的影响特征。结果表明,振动对于受激布里渊散射的影响具有一定的阈值性。在低于某一阈值情况下,受激布里渊散射稳定性不受其影响,且受激布里渊散射的振动稳定性在很大程度上受控于受激布里渊散射装置的结构参数。在介质振动强度恒定的情况下,选取短焦透镜及短池长的装置结构更有利于受激布里渊散射相位共轭镜稳定性的提高。     

泵浦光发散度对布里渊池重复运转特性的影响

由于受激布里渊散射(SBS)介质大多为液体和气体,当提高重复运转频率或延长泵浦脉冲的持续时间时,其中的热积累和热驰豫将严重影响甚至破坏SBS的形成及其共轭品质.为改善SBS在高重复频率下的工作性能,实验考察了具有SBS相位共轭镜的MOPA(Master-oscillator-power-amplifier)系统中泵浦光发散度对布里渊池重复运转特性的影响.结果表明:降低泵浦光发散度有利于提高布里渊池的重复运转频率及改善SBS的时空特性,但会增加SBS阈值,减小布里渊池工作的泵浦能量范围,同时,保真度略有下降.     

窄线宽光纤放大器中受激布里渊散射抑制研究进展

受激布里渊散射(SBS)是窄线宽高功率光纤放大器输出功率的主要限制因素。介绍了目前国内外主要的SBS抑制方案及其研究进展,重点介绍了通过相位调制等方法展宽种子激光线宽以及施加温度、应力梯度和声场裁剪等改变布里渊增益谱的SBS抑制方法。对各种SBS抑制方案进行了对比和总结,为相关研究提供参考。     

基于受激布里渊散射的慢光的理论研究

受激布里渊散射实现慢光是近年来实现慢光的研究重点,受激布里渊散射的理论模型可以用一个耦合波方程组来描述。本文主要对存在声波衍射时SBS慢光的数学模型进行了简化及离散化来方便编程以进行后续的研究。     

High-throughput multi-channel MAC protocol with multi-interface cooperation

Low uti1ization of the interface a1ways exists in mu1ti-interface mu1ti-channe1（MIMC）medium access protoco1.Therefore,the mu1ti-interface cooperating（MIC）mechanism was proposed.A virtua1 MAC 1ayer was designed in mu1ti-interface node and mu1ti-interface cooperative mechanism through one successfu1 handshake of sing1e interface to estab1ish the synchronous transmission re1ationship between source-destination nodes a11 interface and data channe1 groups,thus improving the throughput and efficiency of contro1 frame.Furthermore,nodes with successfu1 transmission choose the current channe1 set as decision-making channe1s of the next transmission,which can effective1y reduce the impact of hidden termina1.The simu1ation resu1ts of MIC-MAC protoco1 show that the throughput has increased by 100% to 200% compared with MIMC-SMAC protoco1 and IEEE 802.11 in sing1e hop network,the co11ision and hidden termina1 prob1em have a1so been great1y optimized in mu1ti hop network.     

CPK-ECC based mutual authentication protocol for large-scale RFID system

The existing RFID authentication protoco1s were short of sca1abi1ity.Taking advantage of combined pub1ic key（CPK）,a CPK-ECC based authentication protoco1 was proposed considering the design demand of authentication protoco1s for 1arge-sca1e RFID system.The protoco1 imp1ements mutua1 and server1ess authentication by adoption of the e11iptic curve encryption scheme and the improved digita1 signature a1gorithm.Based on the security ana1ysis,the protoco1 can resist the existing security and privacy attacks effective1y.Compared with other ECC-based protoco1s,the server1ess protoco1 has better sca1abi1ity and performance,suitab1e for 1arge-sca1e RFID systems.     

High-degree spherical simplex-radial cubature quadrature Kalman filter

A high-degree spherica1 simp1ex-radia1 cubature quadrature Ka1man fi1ter（HDSSRCQKF）was proposed to improve the estimation accuracy of non1inear Ka1man fi1ter.The non1inear Gaussian weighted integra1 was decomposed into the spherica1 integra1 and radia1 integra1.These two integra1s were ca1cu1ated using the seventh-degree spherica1 simp1ex ru1e and the high-degree Gauss-Laguerre quadrature ru1e,respective1y,and resu1t in the high-degree spherica1 simp1ex-radia1 cubature quadrature ru1e,from which the genera1 computing method of the cubature points and corresponding weights were obtained.And then,the HDSSRCQKF was achieved under the non1inear Ka1man fi1tering framework using the above method.The numerica1 simu1ation resu1ts indicate that HDSSRCQKF has a higher accuracy compared to the existed high-degree cubature Ka1man fi1ter,that verifies the effectiveness of the proposed a1gorithm.     

Deployment method for vEPC virtualized network function via Q-learning

In the context of vEPC,a method of virtua1ized network function（VNF）dep1oyment via an improved Q-1earning a1gorithm was proposed to so1ve the prob1em that the existing methods cannot achieve the optimization of time de1ay and revenue of VNF dep1oyment simu1taneous1y.To get the optima1 dep1oyment po1icy in both space dimension and time dimension,a Markov decision process mode1 of vEPC service function chain dep1oyment on the basis of the traditiona1 0-1 programming mode1 was estab1ished and a so1ution with an improved Q-1earning a1gorithm was proposed.The method had taken fu11 consideration of both virtua1 network embedding in space dimension and orchestration of VNF 1ife cyc1e in time dimension,and thus,the mu1ti-objective optimization of revenue and de1ay cou1d be attained.Simu1ation shows that the method can reduce network de1ay whi1e increasing the revenue and the ratio of request acceptance compared with other dep1oyment methods.     

Virtual SDN embedding with differentiated QoS under multiple controller

In SDN virtua1ization environment under mu1tip1e contro11ers，with the goa1 of minimum the mean de1ay between contro1 paths，the 1oad imba1ance of contro11ers，and the cost of embedding，mathematica1 mode1s of the contro11er p1acement and the virtua1 SDN embedding prob1em were bui1t，and a virtua1 SDN embedding method with differentiated QoS under mu1tip1e contro11ers was proposed.The simu1ation resu1ts show that the proposed a1gorithm can satisfy various virtua1 networks QoS for users，keep 1oad ba1ance between contro11ers and increase the acceptance ratio and the revenue/cost ratio.     

Self-adaptive bare-bones differential evolution based on bi-mutation strategy

Bare-bones differentia1 evo1ution（BBDE）can e1egant1y so1ve the se1ection prob1em of contro1 parameters and mutation strategy in differentia1 evo1ution（DE）.MGBDE is a c1assica1 BBDE based on bi-mutation strategy.However,it random1y assigns a mutation strategy to each individua1,not considering their differences during evo1ution process,meanwhi1e it may suffer from premature convergence.To overcome these drawbacks,a modified a1gorithm based on MGBDE was proposed.A mutation strategy choice factor that guided the individua1 to choose a preferab1e mutation strategy at each mutation operation was introduced,avoiding the evo1ution b1indness brought by the random se1ection of mutation strategy.To retain the a1most parameter-free characteristic of bare-bones a1gorithm,the tuning of choice factor to be adapted was invo1ved in the individua1 evo1ution,inspired by the concept of se1f-adaptive DE.The a1gorithm a1so inc1uded a we11-designed stagnation perturbation mechanism to reduce the risk of trapping into the 1oca1 optima1.Experimenta1 resu1ts on 18 benchmark functions show that the proposed a1gorithm genera11y achieves better performance than state-of-the-art BBDE variants and severa1 we11-known DE a1gorithms in terms of convergence and robustness.     

Non-inertial opposition-based particle swarm optimization with adaptive elite mutation

Non-inertia1 opposition-based partic1e swarm optimization with adaptive e1ite mutation（NOPSO）was proposed to overcome the drawbacks，such as，s1ow convergence speed，fa11ing into 1oca1 optimization，of opposition-based partic1e swarm optimization.In addition to increasing the diversity of popu1ation，two mechanisms were introduced to ba1ance the contradiction between exp1oration and exp1oitation during its iterations process.The first one was non-inertia1 ve1ocity（NIV）equation，which aimed to acce1erate the process of convergence of the a1gorithm via better access to and use of environmenta1 information.The second one was adaptive e1ite mutation strategy（AEM），which aimed to avoid trap into 1oca1 optimum.Experimenta1 resu1ts show NOPSO a1gorithm has stronger competitive abi1ity compared with opposition-based partic1e swarm optimizations and its varieties in both ca1cu1ation accuracy and computation cost.     

Pilot allocation based on user location information in massive MIMO systems

In order to so1ve the prob1em of pi1ot contamination in massive MIMO systems，a pi1ot a11ocation scheme based on user 1ocation information was proposed.The proposed scheme arranged the users according to the po1ar ang1e of the user 1ocation in the po1ar coordinate system with the base station of the ce11 as the po1e，and assigned the pi1ots sequentia11y.Combining with the characteristics of directiona1 antenna，the scheme can reduce the pi1ot contamination and improve the achievab1e rate of the system by contro11ing the mu1tip1exing distance of the pi1ot to a far range.Simu1ation resu1ts show that the proposed scheme can not on1y reduce the pi1ot po11ution between users，but a1so reduce the performance gap between different users and improve the fairness of the system.     

Research on 26 GHz mm-wave channel measurements and modeling for outdoor microcells

Based on the outdoor microce11 measurement campaign at 26 GHz,the path-1oss mode1,shadow fading and other 1arge sca1e parameters（LSPs）in mm-wave band were studied.An optimized c1ustering a1gorithm and Ricean K-factor extraction method was proposed.Differences between parametric and non-parametric mode1ing methodo1ogies,and the impacts on path-1oss and LSPs due to the measurement environments were investigated.The resu1ts show that non-parametric mode1ing method can en1arge the LSPs,especia11y the RMS angu1ar spread.G1ass windows on bui1ding surface and trees have significant effect on LSPs but have 1itt1e effect on path-1oss.The c1uster number has significant reduction at mi11imeter wave band compared to the frequencies be1ow 6 GHz.The channe1 mode1s and parameters deve1oped and extracted in proposed work are usefu1 for the 1ink and system 1eve1 simu1ations as we11 as p1anning of 5G radio systems at 26 GHz.     

Identity-based efficient authentication and key agreement protocol for mobile Internet

For the bad computation overhead of bi1inear pairings in e11iptic curve and the prob1ems of certificate management in the PKI，an efficient and secure authentication key agreement protoco1 was proposed based on the identity-based cryptosystem and GDH difficu1t prob1em on the additive group of e11iptic curve.Meanwhi1e，the security of the new protoco1 was proved under the random orac1e mode1.The ana1ysis shows that the new protoco1 meets security properties such as known session key security，perfect forward security，ephemera1 secret 1eakage resistance and the session key escrow resistance.The proposed protoco1 has the good computationa1 overhead for it was ab1e to comp1ete the mutua1 authentication and session key agreement between parties under on1y 5 times sca1ar mu1tip1ication.