Temperature control-free full-mesh wavelength routing network (AWG-STAR) with CWDM AWG-router

AWG-STAR is a star-shaped network that utilizes a uniform-loss cyclic frequency arrayed-waveguide grating (AWG) as a wavelength router to obtain full-mesh interconnection between surrounding wavelength-division-multiplexing nodes. In this paper, we describe a temperature control-free AWG-STAR network that employs a coarse wavelength-division-multiplexing AWG-router. The center wavelength and transmission band of the AWG-router are designed based on the light source wavelength shift that results from changes in operating temperature. The system employs bidirectional transmission to avoid coherent crosstalk from adjacent channels. A cost-effective and small-scale full-mesh network is realized for metropolitan areas.     

Logical Topology Reconfiguration in Full-Mesh WDM Networks (AWG-STAR) Based on Wavelength Routing Technology

Logical Topology Reconfiguration in Full-Mesh WDM Networks (AWG-STAR) Based on Wavelength Routing Technology This paper presents a novel architecture for a logical topology reconfiguration in a wavelength-division multiplexing (WDM) arrayed-waveguide grating (AWG)-STAR network with a star-shaped physical topology and full-mesh path connections for up to$64times64$routes. The network system consists of a data plane in the 1.5-$mu$m wavelength region and an in-fiber control plane in the 1.3-mm wavelength region. On the data plane, each node containing tunable lasers and filters is connected to a$64times64$router. On the control one, a topology-management system with centralized management architecture was constructed. The topology-management system calculates and assigns suitable wavelength paths for each node to be (re)configured for building a new logical topology. This novel feature of the optical-network system enables multitopology (ring, star, mesh, point-to-point, and mixed multiple topologies) (re)configuration, and also node switching from any, to any, topology. The typical topology (re)configuration time of 150 ms was also demonstrated in a constructed testbed system.     

Design theory of long-distance WDM dispersion-managed transmissionsystem

This paper describes a novel design theory of long distance wavelength division multiplexed (WDM) dispersion-managed optical transmission systems. Assuming that the transmission distance, bit rate, and number of WDM channels are initially known, we investigate the optimum dispersion allocation and input power per channel to achieve the minimum channel spacing. Based on the design guidelines for single-channel and multichannel systems, we establish the optimal design strategy. Details of the design procedure are demonstrated for 2.5-, 5-, and 10-Gb/s 10000 km WDM systems by using computer simulations. Next, we study the impact of the fiber dispersion slope on the usable wavelength span, and show that the attainable capacity of the representative 5-Gb/s 10000 km WDM system employing the postcompensation scheme can not exceed 100 Gb/s. Finally, we propose several techniques to approach the ultimate capacity of the WDM system and show that up to 1 Tb/s (200×5 Gb/s) 10000 km system can be implemented without utilizing the in-line dispersion slope compensation scheme. We also discuss the 10 Gb/s-10000 km WDM system employing in-line dispersion slope compensation     

The Photonic Technologies Impact on the Next Generation Network

This paper describes the possible impact of photonic technologies on the next-generation network. With the explosion of the Internet (IP), the capacity demand is increasing exponentially, which exceeds Moor's law. The next-generation IP network should sustain this increase. This paper shows the possible node processing bottleneck even the transmission capacity can be supported by the use of WDM technology. Based on this analysis, the paper proposes a virtual router network as a solution, which applies a logical full-mesh connection based on salient features of photonic network technology. Development of the WDM technology sets the target at 1000 wavelengths on a fiber so that a dynamic wavelength routing function is becoming available. The increase in wavelengths, transparency among wavelengths, and the wavelength routing function can provide an optical path, which forms the base of a logical full-mesh structure and also provides an easy migration scenario from the current network to the next-generation IP network. The possibility is examined by calculation using a bi-directionalloop network as an example. As the foundation of the proposal, the current statusof photonic network technologies is described with future projection.     

Bidirectional unrepeatered 43 Gb/s WDM transmission with C/L band-separated Raman amplification

A novel wavelength arrangement using C- and L-band-separated Raman preamplification is proposed for application to bidirectional unrepeatered transmission systems operating with multiple 43 Gb/s channels. The proposed wavelength allocation makes it possible to greatly mitigate Raman gain depletion by the counter-propagating signals. The authors have achieved bidirectional unrepeatered transmission of 32 /spl times/ 43 Gb/s channels (= 1.28 Tb/s) over 200 km with Raman preamplifiers using the proposed technique. They found that the system performance of bidirectional transmission with C/L band-separated Raman preamplification is degraded by nonlinear interactions between the high power Raman pump lights and the WDM signals. The root cause can be described in terms of nondegenerate four-wave mixing induced by beating between the WDM signals and two longitudinal modes of the Raman pump light. A solution avoiding ND-FWM was demonstrated in a 32 /spl times/ 43 Gb/s transmission experiment.     

Digital Coherent Receiver for Phase-Modulated Radio-Over-Fiber Optical Links

A novel digital signal processing-based coherent receiver for phase-modulated radio-over-fiber (RoF) optical links is presented and demonstrated experimentally. Error-free demodulation of 50-Mbaud binary phase-shift keying (BPSK) and quadrature phase-shift keying data signal modulated on a 5-GHz radio-frequency (RF) carrier is experimentally demonstrated using the proposed digital coherent receiver. Additionally, a wavelength- division-multiplexing (WDM) phase-modulated RoF optical link is experimentally demonstrated. A 3$, times ,$50 Mb/s WDM transmission of a BPSK modulated 5-GHz RF carrier is achieved over 25 km for the WDM channel spacing of 12.5 and 25 GHz, respectively.      

Robust photonic transport network implementation with optical crossconnect systems

We adopt the optical path concept to develop a photonic transport network. Because robustness is critical in a nationwide backbone network, we implement, as a first step, digital frame-based optical path network systems. NTT has developed several types of photonic transport systems. They are an optical path cross-connect system which has little quality of service monitoring large-scale integration circuit for each wavelength; a photonic transport payload assembler-disassembler, which accommodates client signals into optical path payloads and vice versa; and a repeater. The implementation of a PTS is depicted. A network-element-level operating system and an optical-network-level operating system are required to operate the WDM photonic transport network. We introduce a TMN-based network operating system. Finally, an overview of NTT's photonic transport network trial is presented     

OA&M framework for multiwavelength photonic transport networks

Photonic networks based on wavelength division multiplexing (WDM) and optical path technologies are expected to realize flexible, transparent, and cost-effective transport networks with a large transmission capacity. This paper explores the design framework of photonic transport networks taking into consideration the operation administration and maintenance (OA&M) functions required for the successful introduction of WDM systems based on the optical path concept. From the view point of network maintenance, clear distinction is made between the optical path layer and the optical section layer to facilitate accurate and smooth failure localization. The digital multiplexing span between physical multiplexing interfaces at the end-to-end digital nodes should have the same maintenance span as the corresponding optical path. We argue that cooperative maintenance by OA&M functions at both the digital and optical layers can be a practical way of network supervision. A supervisory (SV) signal transfer method and a configuration that is suitable for the terrestrial trunk network are also indicated. As an example, a practical SV system design methodology and an actual procedure developed for a single channel optical transmission system based on optical in-line amplifiers are introduced. Furthermore, application of the developed SV system and network restoration schemes is discussed for future WDM-based photonic networks. The OA&M aspects introduced will be valuable for creating future photonic network systems     

Interferometric crosstalk reduction by phase scrambling

Interferometric crosstalk, arising from the detection of undesired signals at the same nominal wavelength, may introduce large power penalties and bit-error rate (BER) floor significantly restricting the scalability of optical networks. In this paper, interferometric crosstalk reduction in optical wavelength-division multiplexing (WDM) networks by phase scrambling is theoretically and experimentally investigated. Enhancement of 7- and 5-dB tolerance toward crosstalk is measured in a 2.5-Gb/s transmission link of 100 km and 200 km of SSMF, respectively. This result proves the feasibility of optical networking in the local area network/metropolitan area network (LAN/MAN) domain while tolerating the relatively high crosstalk levels of present integrated optical switching and cross-connect technology. Experiment is in good agreement with theory. Recommendations on the use of phase scrambling to reduce crosstalk in WDM systems are given     

Toward wide-scale all-optical transparent networking: the ACTSoptical pan-European network (OPEN) project

The European ACTS project optical pan-European network (OPEN) aims at assessing the feasibility of an optical pan-European overlay network, interconnecting major European cities by means of a mesh of high-capacity optical fiber links, cross-connected through transparent photonic nodes. Both the transmission links and the routing network elements rely on wavelength division multiplexing (WDM) all-optical technologies, such as wavelength translation. This paper presents results obtained in the following domains covered within the project: network topology considerations (optimization and dimensioning); network physical layer simulation; fabrications of packaged functional modules based on advanced optoelectronic devices; laboratory demonstrations of N×10 Gb/s transmission and routing; feasibility of an optical time division multiplexing/WDM (OTDM/WDM) interface; and the field implementation of a 4×4 multiwavelength crossconnect prototype, featuring all-optical space and wavelength routing. This implementation was realized in two cross-border field trials, one conducted between Norway and Denmark and the other between France and Belgium. The final results of the Norway to Denmark field trials are presented, featuring the successful cascade of three wavelength-translating optical crossconnects (OXCs), along with the transmission over 1000 km of a mix of standard/submarine cable links for four channels at 2.5 Gb/s     

All-Raman transmission of 80 × 10 Gbit/s WDM signals with 50GHz spacing over 4160 km of dispersion-managed fibre

All-distributed-Raman amplification in backward-pumped 80 km spans is employed to transmit 80 × 10 Gbit/s non-return to zero (NRZ) wavelength division multiplexed (WDM) signals over 4160 km of a symmetrically-configured dispersion-managed fibre with no forward error correction. At the received bit error rate levels below 10^-9, this is a record capacity-distance product for terrestrial all-Raman systems     

面向电子战射频光传输的宽带射频信号杂散产生机理及优化方法

针对电子战系统的宽带射频信号波分复用传输,通过理论分析给出了微波光子链路中各关键参量对杂散信号的影响规律,提出了非均匀信道间隔分配的除杂优化方法。该方法通过微调各通道的波长,使四波混频产生的杂散频率超过电子战接收机带宽,从而降低杂散对系统的影响。该方案实现简单,且无需改变现有电子战系统架构,具有较好的工程实现性。实验结果表明:与等波长间隔相比,5通道非均匀波分复用信号传输1 km时,在接收机带宽内四波混频引起的杂散得到了显著优化,动态范围提升了26 dB以上。     

Reconfigurable 2.5-Gb/s Baseband and 60-GHz (155-Mb/s) Millimeter-Waveband Radio-Over-Fiber (Interleaving) Access Network

In this paper, we propose a dynamic reconfigurable wavelength division multiplexed (WDM) millimeter-waveband radio-over-fiber (RoF) and baseband access network. We also demonstrate dynamic channel allocation capability of millimeter-waveband optical RoF and baseband signals in WDM access network using a supercontinuum (SC) light source, arrayed-waveguide gratings, and a reconfigurable optical crossconnect switch. The dynamic reconfigurable RoF and baseband network architecture is presented and its features are described. Two 155-Mb/s RoF channels and two 2.5-Gb/s baseband channels are effectively generated, transmitted through 25 km of fiber, switched, and then transmitted again through 2 km of fiber and detected with error-free operation (bit error rate $≪ 10^{-9}$). The proposed architecture allows the RoF and baseband to coexist and is highly scalable, both in terms of channel counts and access point (AP) counts.      

Impact of Fiber Non-linearity in High Capacity WDM Systems and in Cross-Connected Backbone Networks

The rapidly increasing data traffic volumes will demand for very high transmission capacity and network nodes throughput. Wavelength division multiplexing (WDM) technology will be asked to support many channels on the same fiber, both in point-to-point links and in WDM optical networks. The transmission of a high number of wavelength channels in all these systems is a key issue. This paper analyzes this topic, in both high capacity links and optical networks, highlighting the impact of fiber non-linearity, and addressing the main source of impairments. This is done through the use of a semi-analytical model recently upgraded to account for all the contributions deriving from Kerr effects, particularly four-wave mixing and cross-phase modulation. The analysis reveals that more than one hundred of channels at 2.5 Gbit/s can be transmitted in point-to-point links whose length can span until the order of 1000 km, and 32 channels per fiber, at the previous bit rate, can be handled in WDM networks, without dispersion compensation. For a higher number of channels (e.g., 64) dispersion compensation is needed.     

1.6 Tbit/s(40×40 Gbit/s)光通信传输系统

在国家自然科学基金网(NSFCNet)上已实现由400 km×10 Gbit/s传输链路直接升级的一路400 km×40 Gbit/s光传输实验的基础上,采用自行研制的40×40 Gbit/s载波抑制归零(CS-RZ)码多波长光发送源,进行了160 km的1.6 Tbit/s(40×40 Gbit/s)波分复用(WDM)光传输实验。实验结果表明,对于常规中短距离10 Gbit/s传输链路可以直接升级至40 Gbit/s。但是由于40 Gbit/s传输系统的色散容限小于60 ps/nm,而且传输光纤与色散补偿模块的色散斜率不匹配,要实现40通道40 Gbit/s的传输,必须对40个信道分别进行精细的色散补偿。这也说明,对于宽带的40 Gbit/s多波长系统,有必要优化设计或更新传输链路。     

Multiple input detection and digital signal processing for uncooled ONUs in a TWDM-PON with a commercial WDM demultiplexer

A simple uplink transmission scheme with multiple-input direct detection and digital signal processing has been proposed and experimentally demonstrated for the time and wavelength division multiplexed passive optical networks (TWDM-PONs), to allow wavelength drift of lasers at the uncooled optical network units (ONUs). In our experiment, after passing by the commercial 100-GHz WDM demultiplexer, three 10-Gb/s NRZ signals with minimum signal wavelength separation of 50-GHz can be recovered successfully after 50-km standard single-mode fiber (SSMF) transmission. Simulation results are also obtained to analysis the receiver sensitivity at different wavelength separations and discuss methods improving power budget.     

Long-haul WDM transmission using higher order fiber dispersionmanagement

We propose a fiber dispersion management scheme for large-capacity long-haul wavelength division multiplexing (WDM) transmission systems that considers not only second- but also third-order dispersion characteristics using transmission fibers with opposite dispersion signs. It eliminates the waveform distortion of WDM signals that originates from the existence of third-order dispersion, which is a constraint placed on WDM capacity in conventional dispersion management, while reducing the interchannel interaction caused by the interplay of fiber nonlinearity and second-order dispersion. Design concept of the scheme is discussed to show the feasibility of using actual fiber parameters. An experimental investigation on transmission performance regarding the signal pulse format, nonreturn-to-zero (NRZ) and return-to-zero (RZ), and interchannel interaction caused by four-wave mixing (FWM) and cross-phase modulation (XPM) is described for optimizing WDM system performance. It is experimentally shown that RZ pulse transmission is possible without significant spectral broadening over a wide wavelength range in dispersion managed fiber spans. Using these results together with a wideband optical amplifier gain-bandwidth management technique, yields long-distance WDM transmission with the capacity of 25×10 Gb/s over 9288 km     

Performance analysis of multicast routing and wavelength assignment protocol with dynamic traffic grooming in WDM networks

The need for on‐demand provisioning of wavelength‐routed channels with service‐differentiated offerings within the transport layer has become more essential because of the recent emergence of high bit rate Internet protocol (IP) network applications. Diverse optical transport network architectures have been proposed to achieve the above requirements. This approach is determined by fundamental advances in wavelength division multiplexing (WDM) technologies. Because of the availability of ultra long‐reach transport and all‐optical switching, the deployment of all‐optical networks has been made possible. The concurrent transmission of multiple streams of data with the assistance of special properties of fiber optics is called WDM. The WDM network provides the capability of transferring huge amounts of data at high speeds by the users over large distances. There are several network applications that require the support of QoS multicast, such as multimedia conferencing systems, video‐on‐demand systems, real‐time control systems, etc. In a WDM network, the route decision and wavelength assignment of lightpath connections are based mainly on the routing and wavelength assignment (RWA). The multicast RWA's task is to maximize the number of multicast groups admitted or minimize the call‐blocking probability. The dynamic traffic‐grooming problem in wavelength‐routed networks is generally a two‐layered routing problem in which traffic connections are routed over lightpaths in the virtual topology layer and lightpaths are routed over physical links in the physical topology layer. In this paper, a multicast RWA protocol for capacity improvement in WDM networks is designed. In the wavelength assignment technique, paths from the source node to each of the destination nodes and the potential paths are divided into fragments by the junction nodes and these junction nodes have the wavelength conversion capability. By using the concept of fragmentation and grouping, the proposed scheme can be generally applied for the wavelength assignment of multicast in WDM networks. An optimized dynamic traffic grooming algorithm is also developed to address the traffic grooming problem in mesh networks in the multicast scenario for maximizing the resource utilization and minimizing the blocking probability. Copyright © 2011 John Wiley & Sons, Ltd.     

Transmission performance analysis of 8/spl times/10 Gb/s WDM signals using cascaded SOAs due to signal wavelength displacement

We have analyzed the transmission performance of 8/spl times/10 Gb/s wavelength division multiplexing (WDM) signals due to crosstalk in cascaded conventional semiconductor optical amplifiers (SOAs). Using two different methods, the crosstalk over the whole gain bandwidth in SOAs is calculated to be 2-5 dB lower for the positive detuning. Then, transmission performance of 8/spl times/10 Gb/s WDM signals up to 6/spl times/40 km span in terms of receiver sensitivity is estimated over various transmission distances using cascaded SOAs for the positive signal wavelength displacement of 30, 40, and 50 nm. Especially for 50 nm detuning, transmission performances with and without using a reservoir channel are similar to each other. Our results suggest that SOAs can be used as an optical amplifier for displacement larger than 50 nm without using the reservoir channel.     

Multi-stage switching system using optical WDM grouped links based on dynamic bandwidth sharing

A three-stage Clos switch architecture is attractive because of its scalability. From an implementation point of view, it allows us to relax the cooling limitation, but there is a problem interconnecting different stages. This article presents a three-stage switching system that uses optical WDM grouped links and dynamic bandwidth sharing. We call it a WDM grouped-link switch. The introduction of WDM makes the number of cables used in the system proportional to the switch size. Dynamic bandwidth sharing among WDM grouped links prevents the statistical multiplexing gain offered by WDM from falling even if the switching system becomes large. The WDM grouped-link switch uses cell-by-cell wavelength routing. A performance evaluation confirms the scalability and cost-effectiveness of this switch. An implementation of the WDM grouped link and a compact planar lightwave circuit platform is described. This architecture allows us to expand the throughput of the switching system up to 5 Tb/s.