光分组交换网络中多组光正交码组合光标签识别处理及实验

报道了光分组交换网络中基于多组光正交码组合光标签的识别与接收实验,光标签采用了码长为19,码重为3的2组光正交码组合光标签方案.给出了基于多组光正交码光标签的光分组交换网络(MOOC-OPS)基本原理,通过分析指出在MOOC-OPS网络中处理多组在时域上非连续、随机、突发光标签是现实MOOC-OPS关键技术之一.设计出了基于展宽网络和放大器级联方式接收多组低功率窄脉冲(MOOC-OPS网络的光标签)的实验方案,完成了实验电路板制作与实验验证.实验结果表明成功地实现了MOOC-OPS网络中周期为2ns基于多组光正交码光标签脉冲的识别接收,验证了该方案的可行性.     

Separation and insertion of optical bit-serial label in optical packet switching

The bipolar phase-shift-keying (BPSK) optical orthogonal codes (OOCs) are inserted into the optical packet format of bit-serial label. The ultra-fast separation of the label and payload is performed through the auto-correlation pulses indicating the time position at which the optical switch changes the state.The insertion of the new label can also be realized by detecting the auto-correlation pulse at the line rate. Especially, the scheme can be adapted to the asynchronous separation and insertion and realize the variable-length packet switching. The results of simulation verify the feasibility of the scheme.     

Analysis of burst/packet assembly techniques in high-speed optical switching network

In the Optical Burst Switching (OBS) Network, the burst assembly technique is one of the challenging issues in the implementation of the system. It has the influence on the burst characteristic, which gives an impact on the network performance. Burst assembly is the process of assembling incoming data from the higher layer into bursts at the ingress edge node of the OBS network. The burst assembly mechanism must then place these packets into bursts based on some assembly policy. In this paper, the OBS system performance has been observed in simulated 12-node network based on Just-Enough-Time (JET) reservation protocol with various burst assembly techniques under the standard drop policy (DP) and the segmentation policy for contention resolution. The simulation results show that the performance of the proposed Adaptive-Threshold with Fixed Maximum Time Limitation (ATH-FMTL) burst assembly scheme is better than conventional burst assembly schemes in terms of loss probability and average assembly delay. Also, the proposed scheme avoids a sudden increase in the burst size and makes the burst sent out smoother as compared to conventional schemes.     

NOLM-based wavelength conversion with FBG band-pass filter for optical packet switching

Nonlinear-optical-loop-mirror wavelength conversion is studied in details. A set of two-phase-shiftedBragg gratings are introduced into the coverter,serving as a narrow band-pass filter to remove newfrequencies generated by walk-off and to compensate the dispersion. Numerical simulations are performedto validate our method. The results show that the converted pulses after the filter are reshaped and,sometimes, even compressed.     

FWM conversion with pump suppression for filterless optical packet switching applications

The use of a Pump-Suppressed Four Wave Mixing PS-FWM wavelength converter in a wavelength conversion and selection switching scheme is examined and demonstrated. The scheme requires a single 2 × 1 Mach Zenhder Interferometer (MZI) and offers substantial pump suppression and efficiency improvement in terms of optical signal-to-noise ratio. Performance measurements on the combination of PS-FWM wavelength converter with an Arrayed Waveguide Grating (AWG) for passive routing, shows the potentially successful use of the scheme in an ultra-fast wavelength routed optical packet switching scheme where the use of optical filters for the separation of the converted signal from the pump is avoided.     

Seamlessly transformable hybrid packet and circuit switching for efficient optical networks

Efforts in realizing all-optical packet switching are overwhelming in the past decade. While optical packet switching remains an attractive switching paradigm in the long run, technical challenges prohibit it from becoming a practical solution for the ever-growing bandwidth hunger during the next few years. Finding a technically viable way to meet the increasing capacity requirement with good scalability and flexibility becomes a clear pursue for the community. Hybrid packet and circuit switching is considered to be one promising technique in realizing high performance switching at low cost and less energy consumption, by taking the advantage of both packet switching and circuit switching. In this paper, we review existing work in hybrid optical packet and circuit switching. We discuss the key technical challenges in realizing hybrid optical packet and circuit switching. We further introduce our ongoing efforts in building a seamlessly transformable packet/circuit-switching node with hybrid optical and electronic components. We show that in a hybrid node, the scheduling complexity with typical scheduling algorithms may be reduced to half of a node running in full packet switching mode.     

Label swapping and packet transmission of DPSK-labeled PPM signal in optical label switching

A label swapping scheme of an optical labeled signal with differential phase shift keying(DPSK) for label at 2.5 Gb/s and pulse position modulation(PPM) for payload at 40 Gb/s is demonstrated by simulation.Power penalties of ～1.8 and ～0.8 dB are achieved for both the payload and label over 80-km single mode fiber(SMF) transmission.This labeling scheme allows the use of four-wave mixing(FWM) in semiconductor optical amplifier(SOA) to perform label erasure,with advantages of transparence for bit rate,high processing rate,simple architecture,and low cost.Label swapping is demonstrated with appropriate penalties of-3.5 and 0.8 dB for PPM payload and new DPSK label,respectively.To further prove the effectiveness of the proposed scheme,label swapping in the case of using 10-Gb/s DPSK label is also investigated with the power penalties of 6 and 2 dB for PPM payload and new DPSK label.     

A novel scheme of two-dimension time-stacked wavelength-time optical code label for optical packet switching network

A novel scheme of time-stacked optical code label based on optical code division multiple (OCDM) technique for optical packet switching network is proposed, in which two-dimensional wavelength-time OCDM code is used as the optical label. Packet loss rate and system characteristic based on the proposed scheme are studied. Results show that less packet loss rate of proposed scheme can be achieved as compared with that of one-dimension time-stacked optical code label system.     

A novel all-optical label processing based on multiple optical orthogonal codes sequences for optical packet switching networks

This paper proposes an all-optical label processing scheme that uses the multiple optical orthogonal codes sequences (MOOCS)-based optical label for optical packet switching (OPS) (MOOCS-OPS) networks. In this scheme, each MOOCS is a permutation or combination of the multiple optical orthogonal codes (MOOC) selected from the multiple-groups optical orthogonal codes (MGOOC). Following a comparison of different optical label processing (OLP) schemes, the principles of MOOCS-OPS network are given and analyzed. Firstly, theoretical analyses are used to prove that MOOCS is able to greatly enlarge the number of available optical labels when compared to the previous single optical orthogonal code (SOOC) for OPS (SOOC-OPS) network. Then, the key units of the MOOCS-based optical label packets, including optical packet generation, optical label erasing, optical label extraction and optical label rewriting etc., are given and studied. These results are used to verify that the proposed MOOCS-OPS scheme is feasible.     

Research on performance of multicasting in optical packet switched networks

Different multicasting schemes in optical packet switched networks are discussed, including the parallel mode, serial mode, and hybrid mode multicasting schemes. Simulated modeling technique is applied to compare the network-level performance of the three multicasting schemes. A conclusion can be drawn from the results that since the hybrid-mode multicasting scheme can increase the multicast success ratio and reduce the packet retransmission times compared with the other two schemes, it is the best choice for delivering multicasting sessions in the optical packet switched networks.     

Improved optical packet switching structure with recirculation buffer and feedback tunable wavelength converter

The performance of an optical switching network is mainly determined by its core node structure. An improved optical packet switching （OPS） node structure based on recirculation optical fiber delay line （FDL） and feedback tunable wavelength converter （TWC）, and a specific scheduling algorithm for the node structure are presented. This switching structure supports both point-to-point and point-to-multi- points broadcasting transmission with superior capacity expansion performance. Its superiority in packet loss probability is proved by simulation.     

Combining circuit and packet switching using a large port-count optical cross-connect for data center networks

The exponential increase in the data center network traffic has posed new challenges for achieving high throughput, low latency and energy consumption. To address these challenges, this paper presents a novel scheme that combines optical circuit and packet switching technologies together in a single optical cross-connect for data center networks. By utilizing fast tunable linecards and parallel array waveguide grating routers, the optical cross-connect can offer low latency, large scalability and high throughput in datacenter networks. A scheduling technique is designed to simultaneously accommodate circuit switching and packet switching in the optical cross-connect. The physical performance of this optical cross-connect in circuit and packet switching modes is investigated by experiments. In addition, the network performance of the optical cross-connect is evaluated through simulations under a mixed circuit/packet-switched traffic pattern. Results show that the network performance of the optical cross-connect does not degrade significantly with an increase in the number of racks, but it is affected by the circuit-switched traffic proportion.     

An optical multicast packet switching architecture shared with limited-range multi-wavelength converter and full-range wavelength converters

Optical packet switch with multicast capability can inspire a broad range of multipoint to multipoint applications in future optical networks. An optical multicast packet switching architecture, equipped with feedback shared small number of limited-range multi-wavelength converters (LMWCs) and output shared some full-range wavelength converters (FRWCs), is proposed for a wavelength-division multiplexed optical multicast network to improve multicast performance in the paper. The FRWCs are used to overcome the performance degradation in terms of packet loss probability due to only use LMWCs. In the architecture, the two converters are shared by all the multicast packets importing to the optical multicast switch node. A maximum bipartite matching with minimum edges weights strategy was designed to employ fewer wavelength converters and avoid useless degradation of optical signal quality for the architecture to improve the node performance. The simulation results show that the proposed architecture and its wavelength converter scheduling algorithm can reduce the multicast packet loss probability with relatively lesser wavelength conversion cost.     

Novel optical packet switching scheme using OFDM label with one core router and two edge routers

In this paper, we propose and experimentally demonstrate a novel optical packet switching scheme with one core router and two edge routers, in which an orthogonal frequency division multiplexing (OFDM) signal is generated as a label. In this experiment there are two transmission spans, each span consists of 50-km SMF-28 and an erbium-doped optical fiber amplifier (EDFA) without dispersion management. A 10 Gb/s on-off keying (OOK) optical payload and a 2.5 Gb/s OFDM optical label are generated, encapsulated, and transmitted in the first span. And then old label is replaced by new label, the generated new optical packet after transmission over the second span is detached and detected. The transmission performance of the optical label and payload is experimentally investigated at the ingress router, core router and egress router.     

光突发交换中交换矩阵配置时间的影响研究

光突发交换是近几年出现的一种很有前途的交换技术。在光突发交换网络的核心节点中,光交换矩阵是一个关键部件,其配置时间影响到光突发交换网络的性能。这种影响表现在对数据信道可用时间施加了限制。在考虑光交换矩阵配置时间的基础上给出了修正后的LAUC算法,并通过计算机仿真研究了这种配置时间对光突发交换性能的影响。结果表明,光交换矩阵配置时间的增大会导致输出数据信道利用率的降低,进而增大了数据丢失率。     

Nonlinear optical switching matrix

We show that nonlinear directional couplers with variable coupling coefficients can be used to compose a special kind of switching matrix. The switching matrix can be controlled by the signal itself or by a strong pump. Light routing is realized by adjustment of the power of the signal or the pump. Because light routing is based on the optical Kerr effect, ultrafast routing is possible.     

磁流变技术研究及其在光学加工中的应用

介绍了磁流变技术的基本原理及其应用。利用磁流变液在磁场作用下形成的高剪切应力,可以利用磁场形成可变硬度的磁流变液对光学零件进行可控的抛光加工。美国Rochester大学率先进行了应用磁流变液对光学零件进行抛光方面的研究。磁流变抛光获得的表面具有纳米级表面粗糙度。     

Hybrid buffering architecture for packet contention resolution of an optical packet switch

Packet contention is a major issue in optical packet switching network and it is not a trivial task to resolve due to lack of optical RAM technology. In order to resolve contention optical buffering approach is used using fiber delay lines (FDLs). Yet there is a heavy packet loss rate due to unavailability of output port and free FDLs. This paper proposes a hybrid buffering architecture using feed-forward and feedback shared FLDs to resolve packet contention resolution of an optical packet switch. Feed-forward FDLs are used as primary buffer and feedback FDLs are implemented as supplementary buffer. Simulation result shows that proposed hybrid buffering switch achieves packet loss rate between 10⁻¹ and 10⁻² at heavy traffic load (ρ = 0.9) for a 32 × 32 switch using different FDL length.     

Gain-assisted optical switching in plasmonic nanocavities

A plasmonic cavity filled with active material is proposed to explain optical switching. Optical properties, including transmission, response time, and field distribution of on/off state, are numerically investigated. We demonstrate that such a gain-assisted plasmonic structure can achieve optical switching in the nan- odomain and shorten the switching time to the subpicosecond level. Our results indicate the potential application of the proposed structure in optical communication and photonic integrated circuits.