光斑缺碎情形下光学天线光轴对准实验研究

针对同时存在方位偏移及俯仰误差的情况,提出了一种适用于捕获、对准与跟踪系统的光斑检测方法.分析了破碎光斑与高斯完整光斑的位置误差;解决了当光束存在漂移、入射光束与天线视轴不平行同时存在而四象限探测器无法分别探测的问题.最后实验验证了本文方法的有效性,提高了检测的准确度.     

基于轴锥镜对的高光能利用率激光通信天线性能分析

提出一种增加轴锥镜对的同轴反射式光学结构激光发射天线方案,通过对入射光束的光强重新排布,降低同轴反射式结构固有的中心遮拦造成的能量损失,提高光能利用率.运用衍射光学原理分析并模拟了单色高斯光束经过轴锥镜对后传播至天线光阑平面处的光场分布,比较了普通同轴反射式天线和高光能利用率天线在不同入射光束腰半径、不同线遮拦比下的发射光能利用率.结果表明:高光能利用率天线在线遮拦比0.1和0.25的情况下,通过合理调整入射光束腰大小,光能利用率分别可达到99%和96%以上,远高于传统的同轴反射式天线.分析了高光能利用率天线发射光束的远场光强分布,发现其进入接收天线口径内的光场可近似为平顶分布.     

基于少模光纤单模工作的量子-经典信号同传

考虑到少模光纤单模工作时具有低非线性以及损耗、色散保持特性,提出基于少模光纤单模工作的量子-经典信号同传方案.使用Optisystem构建了基于少模光纤单模工作的量子-经典信号同传模型,分析了其传输性能,并与现有的基于单模光纤的量子-经典信号同传模型进行了对比.结果表明所提模型可以有效降低现有模型中的非线性效应和信号串扰,将误比特率降低了两个数量级,显著提高了信号的传输质量,可用于量子保密通信大规模网络化.     

灰霾粒子与水云粒子不同混合方式对量子卫星通信性能影响

为了研究混合粒子的不同混合方式对星地量子卫星通信的影响,根据灰霾粒子与水云粒子的谱分布函数,以及不同混合方式下的消光系数,提出了外混合方式中星地量子信道衰减的计算关系,建立了内混合方式中的Core-shell信道衰减模型;分析了在不同混合方式下,混合粒子的粒径比与信道平均保真度、信道误码率之间的定量关系.仿真结果表明,当混合粒子的粒径比分别为0.2和0.8时,外混合粒子对应信道容量、信道平均保真度、信道误码率分别为0.39和0.27,0.8和0.8,0.003和0.009;内混合粒子对应信道容量、信道平均保真度、信道误码率分别为0.8和0.21,0.94和0.81,0.018和0.021.由此可见,灰霾粒子和水云粒子的不同混合方式对量子卫星通信性能的影响有显著差别.因此,在实际的量子卫星通信系统中,应根据混合粒子的不同混合方式自适应调整系统的各项参量,以提高星地量子通信链路的可靠性.     

星间激光通信终端光学天线的隔离度

为满足星间激光通信对高隔离水平光学天线的要求,实现对光学天线隔离度的仿真分析和优化,提出了一种将红外系统冷反射的特征控制量YNI值作为衡量光学元件表面后向反射能量强度,并控制光学天线优化以提高隔离度水平的方法。在Light Tools软件中为某激光通信终端的卡塞格林天线创建了实体模型,通过仿真分析得出了各元件表面的后向反射率。在ZEMAX软件中以增大各元件表面的YNI值为目标优化天线结构。对比优化前后的结果,系统的后向反射率从3.068 8×10~(-4)减小到1.075 5×10~(-5),隔离度从-35.13 d B减小到-49.68 d B。优化后的卡塞格林天线具备较高的隔离度水平,可用于星间激光通信。     

Integrated wireless communications and wireless power transfer: An overview

As an important application of the fifth generation (5G) mobile communication systems, Internet of Things (IoT) has attracted worldwide research interests. Since most of the communication devices in IoT are powered by batteries, these devices always have limited operation time. Wireless power transfer (WPT) technology, which can transfer power over a wireless medium (without any wires), can avoid the need to manually replace or recharge the batteries of the wireless devices in IoT. For electromagnetic (EM) radiation-based WPT, since radio-frequency (RF) signals that transport energy can at the same time be used for wireless communications, integrated wireless communications and WPT becomes a new research area which has attracted great research interests. In this paper, we first introduce two main research paradigms for integrated wireless communications and WPT, i.e., simultaneous wireless information and power transfer (SWIPT) and wireless-powered communication network (WPCN). Then we provide an overview of the state-of-the-art of both SWIPT and WPCN, respectively. Finally, we point out the new and challenging future research direction.     

Decode-and-forward with quadrature spatial modulation in the presence of imperfect channel estimation

The performance of quadrature spatial modulation (QSM) multiple-input multiple-output (MIMO) system with cooperative decode and forward (DF) relays is analyzed in this paper. QSM is a new MIMO transmission technique that enhances the overall performance of conventional spatial modulation through exploiting quadrature spatial dimension. A practical scenario is considered where the channel is estimated at the relays and the destination and the impact of channel estimation error is investigated. Two cooperative systems are considered in the study. In the first system, multiple single-antenna DF relays are assumed, whereas, in the second system, single multiple-antennas DF relay is considered. For both systems, an analytical expression for the pair wise error probability (PEP) is obtained. As well, an asymptotic expression for the PEP at high and pragmatic signal to noise ratio is derived. Derived expressions are used to provide an upper bound on the average bit error ratio. The derived analysis is corroborated through Monte Carlo simulations and results demonstrate a close-match for a wide range of SNR values.     

基于高维突变模型的海上通道安全预警研究

为了在海上通道突发事件发生前给出可能的危险等级,减少海上通道突发事件造成的损失和提高海上通道预警与应急管理能力,本文针对海上通道安全突发事件的复杂性,提出一种历史案例分析与高维突变级数相结合的新方法。首先,通过对历史突发事件案例的统计分析,得出海上通道安全的主要风险源因素,并由此建立了海上通道安全预警指标体系。其次,将突变级数法在高维指标应用方面进行了推广,建立海上通道安全预警模型,并根据历史案例数据计算模型的预警阈值。最后,选取了实际案例对预警模型进行了检验,检验结果表明模型可以对海上通道突发事件进行有效预警。     

An Improved Quantum Information Hiding Protocol Based on Entanglement Swapping of χ-type Quantum States

In 2011, Qu et al. proposed a quantum information hiding protocol based on the entanglement swapping of χ-type quantum states. Because a χ-type state can be described by the 4-particle cat states which have good symmetry, the possible output results of the entanglement swapping between a given χ-type state and all of the 16 χ-type states are divided into 8 groups instead of 16 groups of different results when the global phase is not considered. So it is difficult to read out the secret messages since each result occurs twice in each line (column) of the secret messages encoding rule for the original protocol. In fact, a 3-bit instead of a 4-bit secret message can be encoded by performing two unitary transformations on 2 particles of a χ-type quantum state in the original protocol. To overcome this defect, we propose an improved quantum information hiding protocol based on the general term formulas of the entanglement swapping among χ-type states.     

新型小尺寸窄带偏振分光器在光纤通信中的应用

在光纤通信中,为了在不改变调制波长范围的基础上仍能实现更多数据通道的波分复用,设计了一种新型的小尺寸窄带偏振分光器,用于对现有的数据通信网络进行扩容以及提高光信号的信噪比。在该分光器上蒸镀了两种新设计的膜系,一层是窄带滤光膜,另一层是偏振分光膜。采用TFCalc软件仿真,设计结果中窄带滤光膜的带宽约为0.4 nm,偏振分光膜在1 530～1 560 nm范围内对p光的通透性能优于99.8%。基于以上膜系设计在BK7光学玻璃上实际制备两组膜系,实验采用Agilent 8164-A型光波测量系统对经过膜后的光进行光谱分析。结果显示,窄带滤光膜的实际带宽优于0.4 nm,增益平坦度小于-0.05 dB,相比现有常见的0.8 nm滤光膜具有更窄的带宽,可以实现在调制波长范围不变的条件下增大波分复用的数据通道总量。偏振滤光膜的实际p光透光率为99.6%,相比仿真值略低,但仍优于设计要求,相比传统分光器的光信号强度保留效果更好,具有更高的信噪比。综上所述,该分光器具有更好的应用价值和实用意义。