Extensible router for a quantum key distribution network

Building a quantum key distribution network is crucial for practical quantum cryptography. We present a scheme to build a star topology quantum key distribution network based on wavelength division multiplexing which, with current technology, can connect at least a hundred users. With the scheme, a 4-user demonstration network was built up and key exchanges were performed.     

High Speed Demultiplexer Based on a Three-Wavelength SLA

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Two-dimensional shift-orthogonal random-interleaving phase-code multiplexing for holographic data storage

A novel phase encoding technology for phase-code multiplexing in holographic data storage (HDS) system called two-dimensional shift-orthogonal random-interleaving (2-D SORI) phase encoding is proposed. Compared with the traditional one-dimensional orthogonal phase-code multiplexing methods, the 2-D method is less sensitive to the variations of the diffraction amplitude and to the phase error of the phase mask. Phase masks for the 2-D SORI phase-code multiplexing can be generated by shifting an elaborately designed phase plate at a certain step, which can avoid the use of a high-cost phase spatial light modulator for the generation of multiple orthogonal phase masks. The cross-talk arising from the systematic phase defects of the static phase modulator is eliminated by the shift operation of the phase plate. Phase codes are interleaved under a predetermined random mapping rule to prevent unauthorized users from accessing the data and eliminate the Bragg degeneration cross-talk. A 2-D SORI phase plate with the size of 5.12 mm × 10.24 mm is designed and fabricated, from which 128 orthogonal phase patterns are generated. The feasibility of the 2-D SORI phase-code multiplexing method for HDS is experimentally demonstrated.     

Higher-order Gabitov–Turitsyn equation for solitons in optical fibers

The higher-order multiple-scale asymptotic analysis is carried out for the Gabitov–Turitsyn equation that governs the propagation of dispersion-managed solitons through optical fibers. The averaged equation, with the consideration of higher-order terms, provides an in-depth understanding of the soliton propagation through an optical fiber. The polarization preserving fibers as well as birefringent fibers are considered in this paper. Finally, the study is extended to the case of multiple channels, namely dispersion-flattened fibers.     

The cost benefits of multi-layer architecture with multi-granularity switching in optical networks

The benefits of using multi-granularity switching to reduce the number of ports, including both electronic and optical ports, have been investigated. A novel multi-layer ring architecture with multiple switches is proposed and two general equations to count the number of ports are derived. Comparisons are made between the multi-layer multi-granularity switching (MM-XC) architecture and the reported architectures: multi-switching (M-XC) and single switching (S-XC) architectures. The results show that the M-XC or S-XC architectures can be deduced from the MM-XC architecture and the latter architecture can achieve more considerable savings of the port count compared to the former.     

Algorithm for Scheduling Variable-Length Messages in WDM Networks

In this paper, we develop and analyze a simple algorithm for scheduling variable length messages in WDM networks with a passive star coupler. We base our schemes on a star topology with centralized control and use a scheduling algorithm similar to the process management in UNIX system. Every node and message have a scheduling priority associated with them. By comparing our algorithm with random select algorithm, we find that significant improvement in performance can be achieved with very little extra cost.     

高功率准分子激光系统光学设计

回顾并介绍了高功率准分子激光系统设计中需要综合考虑的两项主要技术——像传递技术和角多路技术。讨论了照明方式和激光振荡源的光束整形在激光系统成像光路设计中的重要作用,对多路放大技术及角多路放大技术形式进行了系统分析。多路激光非相干合束是角多路技术和成像技术对高功率准分子激光系统光学设计提出的特殊要求,在简要分析了透射阵列和反射式望远物镜两种实现多路激光合束的打靶光学系统基础上,提出了一种利用反射式打靶光学系统和一套光学延迟线阵列来同时实现角多路编码和解码的新型光路布局,给出了初步设计方案。     

“天光一号”平滑化角多路系统的建立

采用诱导空间非相干（FEISI）的平滑方法结合传递傅里叶面的技术,建立了一套平滑化六束角多路系统。该系统输出总能量158 J,能量稳定度约4％,输出脉冲宽度25 ns,靶面有效焦斑直径400 μm,焦斑均匀性1.6％,激光功率密度3.7×1012 W/cm2。     

Statistical Degree Distribution Design for Using Fountain Codes to Control the Peak-To-Average Power Ratio in an OFDM System

Utilizing fountain codes to control the peak-to-average power ratio (PAPR) is a classic scheme in Orthogonal Frequency Division Multiplexing (OFDM) wireless communication systems. However, because the robust soliton distribution (RSD) produces large-degree values, the decoding performance is severely reduced. In this paper, we design statistical degree distribution (SD) under a scenario that utilizes fountain codes to control the PAPR. The probability of the PAPR produced is combined with RSD to design PRSD, which enhances the smaller degree value produced. Subsequently, a particle swarm optimization (PSO) algorithm is used to search the optimal degree value between the binary exponential distribution (BED) and PRSD distribution according to the minimum average degree principle. Simulation results demonstrate that the proposed method outperforms other relevant degree distributions in the same controlled PAPR threshold, and the average degree value and decoding efficiency are remarkably improved.     

空间层叠矩形阵列式角多路解码光路设计

根据角多路技术原理,提出了一种矩形阵列空间层叠形式的解码光路结构和先分组解码再组内解码的两步解码方式,并针对本实验室的高功率准分子激光系统给出了具体的解码光路设计实例。该方法具有解码精度高,设计误差小,与光路准直、激光参数测量系统等兼容性好,便于加工制作和安装调试等优点。