多跳相干探测光谱幅度码标记交换系统传输特性分析

提出了一种基于标记栈技术的两跳相干探测光谱幅度码(SAC)标记交换系统.利用仿真软件,搭建了包含两个转发节点、两个156 Mb/s光谱幅度码标记、与40 Gb/s差分正交相移键控(DQPSK)净荷的光标记交换系统.利用接收光功率与光信噪比(OSNR)分析系统传输性能,并得到结论:经两个节点传输后,标记与净荷产生的功率代价与OSNR代价均未超过3 dB.     

160 Gb/s variable length packet/10 Gb/s-label all-optical label switching with wavelength conversion and unicast/multicast operation

We report on the first demonstration of all-optical label switching (AOLS) with 160 Gb/s variable length packets and 10 Gb/s optical labels. This result demonstrates the transparency of AOLS techniques from previously demonstrated 2.5 Gb/s to this 160 Gb/s demonstration using a common routing and packet lookup framework. Packet forwarding/conversion, optical label erasure/re-write and signal regeneration at 160 Gb/s is achieved using a WDM Raman enhanced all-optical fiber cross-phase modulation wavelength converter. It is also experimentally shown that this technique enables packet unicast and multicast operation at 160 Gb/s. The packet bit-error-rate is measured for all optical label switched 16 /spl times/ 10 Gb/s channels and error free operation is demonstrated after both label swapping and packet forwarding.     

扫频相干探测光谱幅度码标记交换系统的传输性能分析

基于光谱幅度码(SAC)标记的生成原理,利用扫频相干探测技术,搭建对156Mbit/s SAC标记进行识别的SAC标记交换系统。加载40Gb/s强度调制(IM)净荷信息后,分别对背靠背、40km和80km传输距离下,本振光源(LO)线宽、发射功率以及净荷与标记频率间隔对标记接收质量的影响进行仿真分析。同时分析接收光功率(ROP)、光信噪比(OSNR)、标记与净荷频率间隔对净荷误码(BER)特性的影响。结果表明:传输40 km、80 km后,标记接收眼高度(EH)与背靠背系统相比差别较小,且都能达到-0.6 dB左右;同时,传输80 km后,当净荷BER为10-9时,其ROP与OSNR分别为-17.8dBm和14.5dB。     

160-Gb/s All-Optical Packet-Switching With In-Band Filter-Based Label Extraction and a Hybrid-Integrated Optical Flip-Flop

An in-band labeling scheme with filter-based label extraction is employed for very high-speed optical packet-switching. The scheme shows a potentially high scalability, up to 25 labels in a 5-nm bandwidth packet using commercial arrayed waveguide gratings as the label processor. Switching is demonstrated using packets with two different 9-ns labels, 6.4- and 4.6-ns guard times, and 56.8-ns payload at 160 Gb/s. The system uses a tunable optical filter as the label extractor, a hybrid integrated optical flip-flop, and a high-speed semiconductor-optical-amplifier-based wavelength converter. Error-free operation is achieved with acceptable error penalties.     

Transmission performance of implicit optical label switching system with coherently detected spectral amplitude code labels

A new optical label switching system with coherently detected implicit spectral amplitude code (SAC) labels is proposed in this paper. The implicit SAC labels are recognized using a frequency-swept local light source oscillator. An explicit SAC-label switching system with 40 Gbit/s intensity modulation (IM) payloads and 156 Mbit/s label and an implicit SAC-label switching system with 2.5 Gbit/s IM payloads and 156 Mbit/s label are both considered. Label and payload bit error rate (BER) performance is assessed and compared by simulations. The results reveal that after 80 km transmission and at the BER of 10-9, the received optical power (ROP) values of label and payload are -8.3 dBm and -23.5 dBm in implicit SAC-label switching system, respectively, while those are -18.2 dBm and -18.6 dBm in explicit SAC-label switching system, respectively. As a result, the payloads of 40 Gbit/s and 2.5 Gbit/s in explicit/implicit SAC-label switching system have little influence on the received payload quality at the BER of 10-9 after 80 km transmission. Finally, a payload of 40 Gbit/s can obtain 12.5 dB optical signal-to-noise ratio (OSNR) after 80 km transmission.     

A novel architecture of optical code label processing in parallel designed for all optical routing system

A novel architecture of optical code label routing is designed based on optical code division multiplexing techniques, which performs the data packet forwarding and processing in parallel with a way of making the label and payload encoded and decoded separately. It uses optical polarity characteristics to realize the separation of the label and payload, employs fiber Bragg grating to encode/decode the label and payload so as to process them in parallel, and makes the forwarding and routing process realized in the optical domain. In the core router, the separation of the label and payload guarantees that the switch processing only includes the short label code recognition, without processing the payload. The payload recognition is carried out in the edge router. Thus, the router can simplify the processing of encoding and decoding in the core router, accelerating the switching, and increase the throughput greatly. Moreover, the novel routing scheme not only supports the varying of data packets, transparent transmission, fine granularity switching, and so on, but also is suitable for the aggregation of data service. It is attractive for the future development of all optical routing.     

Payload-Label Tolerance in Subcarrier Multiplexing Optical Label Switching Routers

We present a theoretical and experimental evaluation of the tolerance between optical labels and payloads in an optical router with 10-Gb/s packet payload and 155-Mb/s subcarrier multiplexing encoded label. The label processing functions are described in detail and alignment aspects are precisely evaluated by changing separately the arrival time of both label and payload signals. For the first time to our knowledge the experimental verification allows us to evaluate the delay tolerance in the process of coding the baseband label onto the optical packet without affecting the normal operation of the router. According to the router parameters, the maximum range of misalignment is estimated to be around 100-120 ns.     

Advanced Subcarrier Multiplexed Label Swapping in Optical Packet Switching Nodes for Next Generation Internet Networks

This paper presents the recent achievements and main results of the optical packet switching node with label swapping capabilities that was developed in the framework of the IST-LABELS project. The implemented functionalities allows the routing and forwarding of optical packets at 10 Gb/s based on the information conveyed in the 18 GHz-subcarrier multiplexed (SCM) label at 155 Mb/s. Specific functions of the optical packet switching demonstrator such as label extraction and rewriting are based on high-performance fiber Bragg grating filters (FBG) whereas semiconductor optical amplifier (SOA) based wavelength conversion allows payload 2R regeneration. Advanced aspects implemented in the high speed electronic control unit such as traffic shaping, multicast, and for the first time to our knowledge, a contention resolution algorithm with priority processing are thoroughly described in this paper. This paper also presents simulations exploring the effect of these advanced features in the global performance of an optical packet switched network. In particular, we found that the contention resolution algorithm based on parallel converters with 16 wavelengths contributes to improve up to four orders of magnitude the packet loss rate for low traffic loads whereas the improvement from traffic shaping policies was of 1 order of magnitude for both low and medium traffic loads. Along with the experimental results, the feasibility of the approach as the basis for the next generation internet networks is demonstrated.     

All-Optical Asynchronous Serial-to-Parallel Converter Circuit for DPSK Optical Packets

We propose a novel asynchronous all-optical circuit for extraction and serial-to-parallel conversion of label bits from differential phase-shift keying (DPSK) packets. The circuit requires only two optical switches regardless of the number of bits to be extracted and parallelized from the packet. Experimental evidence of practical use of the circuit to four bit labels at 10 Gb/s is provided. The circuit is scalable with the number of bits, operates at low input power, and is suitable for photonic integration. The asynchronous nature of the circuit allows us to efficiently extract/read one specific label field of variable length without processing the entire label, leading to a simplified architecture of the label processing circuit     

Design and experimental demonstration of a variable-length optical packet routing system with unified contention resolution

This paper presents theoretical design, network simulation, implementation, and experimental studies of optical packet routing systems supporting variable-length packets. The optical packet switching network exploits unified contention resolution in core routers in three optical domains (wavelength, time, and space) and in edge routers by traffic shaping. The optical router controller and lookup table, implemented in a field-programmable gate array (FPGA), effectively incorporates the contention resolution scheme with pipelined arbitration of asynchronously arriving variable-length packets. In addition, real-time performance monitoring based on the strong correlation between the bit-error rates of the optical label and those of the data payload indicates its application in optical time-to-live detection for loop mitigations. Successful systems integration resulted in experimental demonstration of the all-optical packet switching system with contention resolution for variable-size packets.     

改进型双二进制归零码信号在标记交换系统中的新应用

提出以改进型双二进制归零码(MD-RZ)信号作为标记,分别采用差分相移键控非归零码(NRZ-DPSK)信号和差分正交相移键控非归零码(NRZ-DQPSK)信号作为载荷进行正交调制的新方案.然后提出了一种从标记信号中提取和恢复时钟的简单方案.比较了背对背系统中2.5 Gbit/s的MD-RZ标记叠加到10 Gbit/s的NRZ-DPSK载荷和20 Gbit/s的NRZ-DQPSK载荷上的频谱特性,证明了MD-RZ标记占空比越大,光分组信号的频带利用率越高.采用传统的二进制强度调制-直接检测(IM-DD)系统的接收机检测得到了背对背系统中不同占空比的2.5 Gbit/s MD-RZ标记的眼图.结果表明,若采用色散补偿技术,两种光分组信号中的MD-RZ标记能够在长距离传输时克服接收端眼图的失真;当入纤功率值高于18 dBm时,占空比取值越大,MD-RZ标记的眼开度代价具有越高的传输鲁棒性.     

Flow aggregated, traffic driven label mapping in label-switchingnetworks

Label-switching technology enables high performance and flexible layer-3 packet forwarding based on the fixed-length label information that is mapped to the layer-3 packet stream. A label-switching router (LSR) forwards layer-3 packets based on their layer-3 address information or their label information that is mapped to the layer-3 address information. Two label-mapping policies have been proposed. One is traffic driven mapping, where the label is mapped for a layer-3 packet stream of each host-pair according to the actual packet arrival. The other is topology driven mapping, where the label is mapped in advance for a layer-3 packet stream toward the same destination network, regardless of actual packet arrival to the LSR. This paper evaluates the required number of labels under each of these two label-mapping policies using real backbone traffic traces. The evaluation shows that both label-mapping policies require a large number of labels. In order to reduce the required number of labels, we propose a label-mapping policy that is a combination of the two label-mapping policies above. This is traffic-driven label mapping for the packet stream toward the same destination network. The evaluation shows that the proposed label-mapping policy requires only about one-tenth as many labels as the traffic-driven label mapping for the host-pair packet stream and the topology-driven label mapping for the destination-network packet stream     

All-optical label processor/erasure for label swapping of 12.5 Gbit/s spectrally separated bit-serial DPSK label and payload

A novel all-optical label processor/erasure for DPSK spectrally separated label and payload is demonstrated. Experimental results show the recognition of two different labels at 12.5 Gbit/s at distinct outputs, while the label is simultaneously erased allowing for a new label insertion. The low power and asynchronous label processor/erasure can be scaled to distinguish a larger number of labels, to operate at higher bit rate, and then can be potentially used in an optical label switching network.     

An optical IM/FSK coding technique for the implementation of a label-controlled arrayed waveguide packet router

In this paper, we present a new concept of optical packet/burst switching suitable for generalized multiprotocol label switched (GMPLS)-based optical networks. In such networks, optical labeled switched paths are being established in a similar way as label-switched paths in MPLS. We use a wavelength label as well as an orthogonally modulated label, with respect to the payload modulation format, and which is encoded using either frequency-shift keying (FSK) or differential phase-shift keying (DPSK). Wavelength is used for switching in the node, whereas the orthogonal label defines the label-switched path. We present both simulation and experimental results to assess transmission performance of the proposed combined modulation scheme. In addition, we propose a suitable optical node architecture that can take advantage of this stacked label concept. Toward this, we use widely tunable wavelength converters to efficiently route IM/FSK (or IM/DPSK) optically labeled packets in an arrayed-waveguide grating (AWG)-based node structure. We present performance simulation results in terms of packet loss ratio and internal block probability. Internal blocking is an inherent problem of AWG optical routers, and a specific wavelength assignment algorithm has been developed to minimize it. Finally, the feasibility of IM/FSK transmission is experimentally demonstrated over an 88-km single-mode fiber span, and novel aspects of FSK generation and detection techniques are presented.     

基于正交调制PolSK/Inverse-RZ的光标记技术

光标记技术是一种实现光分组交换的重要技术.文章提出并用实验验证了一种基于正交调制PolSK/Inverse-RZ的新型光标记方案,该方案用Inverse-RZ作载荷信号,用PolSK作标记信号.由于Inverse-RZ信号在比特"1"和比特"0"时都具有光功率,在PolSK信号检测时信息一直保持着,因此通常使用ASK信号标记的技术在消光比方面的限制被解决了.     

Label swapping versus label preserving in packet switched networks: Impact on the label space size

In recent years, switching and networking solutions exploiting all-optical nodes are gaining increasing interest to achieve the target of ultrawide-bandwidth and low-latency packet or burst processing. On the one hand, many prototypes, validated by experimental demonstration of all-optical label processing solutions, have been developed. On the other hand, the primitive available technology for performing label processing poses several constraints on the label structures; this in turn significantly impacts the traffic engineering aspects of such a network.In this paper, the label assignment problem is studied in a network that makes forwarding decision based on optical packet labels and formulated independently of any technology. Specifically, the problem of assigning labels to identify the label switched path (LSP) packets in a unique and disjoint way is defined, with the objective of optimally minimizing the label space size (i.e. number of labels, or bits, required to uniquely identify the LSPs). The network scenarios where (i) labels have local point-to-point significance (i.e. the label is swapped when traversing each node), and (ii) labels have end-to-end significance (i.e. the label is preserved along the LSP traversing multiple nodes) are both investigated. For both scenarios, labels can be uniquely identified at each node or at each node-port. The label assignment strategies for all the possible scenarios are investigated.Both theoretical and practical methods, i.e. integer linear programming formulations and heuristics, respectively, are used to assess the efficiency of the proposed label preserving solution. Numerical results show that, for a significant set of network topologies, the label space size increase experienced by networks with label preserving capabilities is limited or negligible in both per-node and per-port label identification.     

All-optical label and payload separator for a time-serial RZ-IM/IM scheme

We demonstrate an all-optical label and payload separator based on nonlinear optical signal processing with a semiconductor optical amplifier. The separator handles return-to-zero intensity modulated packets with high bandwidth efficiency utilization.     

OPERA: an optical packet experimental routing architecture withlabel swapping capability

This paper describes experimental and simulation results of the optical packet experimental routing architecture (OPERA) project. The OPERA network is based on a novel optical network interface router design that is optically regenerative and supports optical Internet protocol related functions including label swapping, packet routing and forwarding operations and wavelength reuse. Routing is based on subcarrier multiplexed header addressing, packet-rate wavelength conversion, and arrayed waveguide router technology. The routers are cascadable and use a unique double stage wavelength converter that supports header regeneration/replacement and maintains the payload extinction ratio. This approach overcomes dispersion limitations normally encountered using double sideband subcarrier multiplexing across a network. A discrete time simulation of the physical transport in an 8-hop network is reported. Multihop routing is experimentally demonstrated between two all-optical nodes and three input-output (I-O) ports of a waveguide grating array router. Packet-rate subcarrier header processing and wavelength conversion between six wavelengths is shown with high signal-to-noise ratio (SNR) of recovered payload and headers at each hop     

100-Gb/s Packet Signal Generation With Spectral Efficiency Larger Than 1 bit/Hz/s

We have experimentally demonstrated how to generate 100-Gb/s packet signals with spectral efficiency higher than 1bit/Hz/s for the first time. The optical packet with 3.125-Gb/s label and 100-Gb/s return-to-zero differential quadrature phase-shift-keying payload are generated by using optical carrier-suppression and separation and vestigial sideband filtering techniques. The performance of transmission and label erasure has also been evaluated.     

A novel IP with MPLS over WDM-based broad-band wavelength switchedIP network

This paper presents a new technology for constructing IP over photonic systems. An IP with multiprotocol label switching (MPLS) over wavelength division multiplexing (WDM)-based broad-band IP network architecture and protocol is proposed and analyzed in this paper, which supports variable-length IP-like optical packet label switching and optical virtual path routing. This system tries to merge into one layer the functionalities of the wavelength switching, SONET mux/demux, and IP routing, and is sometimes known as the concept of optical MPLS. The label banding, forwarding/switching process, and node architecture of the proposed network are discussed and studied. A unique as well as important function of a lambda/label edge router (LER) is a flow assembly device that can encompass MPLS' forward equivalence classes, label stacking, and label switching path aggregation function. At the same time, a particular function of the core label switching router is wavelength merging. A fiber delay line is used to delay the data stream in order to process the label information and resolve contention. Transmission bit error rate measurements of the baseband data stream and back-to-back is also demonstrated to show its feasibility