Dense Wavelength Division Multiplexing Technology Research Articles

WDM PONs based on colorless technology

Wavelength Division Multiplexing (WDM) Passive Optical Network (PON) is foreseen to be part of the Next Generation Passive Optical Networks. Business and mobile fronthaul networks already express the need to develop WDM PONs in the access segment. Fixed wavelength transceivers based on Coarse WDM are already available to respond to today’s market needs but Dense WDM technologies will be needed and colorless technologies are essential to provide simple and cost-effective WDM PON systems. We propose in this paper to demonstrate the capabilities of a DWDM PON system prototype based on self-seeded RSOAs and designed to transmit CPRI over 60km of fiber at 2.5Gbit/s.

THE METHODOLOGY OF INFORMATION CAPABILITIES ESTIMATION FOR FIBER-OPTICS COMMUNICATION

The method for assessing a channel capacity and productivity of fiber-optic communication line (FOCL) based on the DWDM (Dense Wavelength Division Multiplexing) technology is proposed. The interrelation between noise-immunity factors and information characteristics of FOCL is highlighted.

Optical Add Drop Multiplexer (OADM) Based on Dense Wavelength Division Multiplexing Technology in Next Generation Optical Networks

The OADM based on DWDM technology is moving the telecommunications industry significantly closer to the development of optical networks. The OADM can be placed between two end terminals along any route and be substituted for an optical amplifier. Commercially available OADMs allow carriers to drop and/or add up to multi channels between DWDM terminals. By deploying an OADM instead of an optical amplifier, service providers can gain flexibility to distribute revenue–generating traffic and reduce costs associated with deploying end terminals at low traffic areas along a route. The OADM is especially well-suited for meshed or branched network configurations, as well as for ring architectures used to enhance survivability. Moreover, An optical add/drop multiplexer with tunable bandwidth offers several potential advantages, including optical performance monitoring and dynamic bandwidth allocation. This paper has proposed OADM for high transmission bit rates and products in next generation optical communication networks based on dense wavelength division multiplexing for different fiber link lengths at room temperature for best performance efficiency.

DWDM 기반 차세대 광 인터넷 망에서 VS기반의 차등화된 멀티캐스트 라우팅 및 파장할당 알고리즘 연구

지난 수 십 년간 통신 기술의 발전과 웹 서비스의 팽창은 인터넷 사용자 수의 폭발적인 증가와 화상회의, 가상 증감 현실, 인터넷 게임 등 실시간 멀티미디어 멀티캐스트 서비스의 급격한 증가를 초래했다. 고밀도 파장분할다중화기술에 기반한 DWDM(Dense-Wavelength Division Multiplexing) 기술은 인터넷 사용자의 증가와 그에 따른 대역폭 요구를 수용하기 위한 방안으로 국가나 글로벌 영역 범위의 차세대 인터넷망 구현을 위한 백본망 기술로 여겨지며, 이러한 DWDM 전달망에서는 멀티캐스트 연결 요구에 대해 최적의 경로를 선택하고 선택된 경로에 효율적으로 파장을 할당하는 멀티캐스트 RWA(Routing and Wavelength Assignment) 문제가 파장 대역폭의 효율적인 활용 측면에서 매우 중요하게 다루어지고 있다. 주어진 파장 수 환경에서 최대한 많은 수의 멀티캐스트 연결을 달성하는 문제는 일반적으로 Non -deterministic Polynomial-time-complete 문제로 여겨지는 데, 본 논문에서는 가상소스를 기반으로 노드의 능력에 따른 차등화로 우선 순위를 적용하여 휴리스틱하게 멀티캐스트 라우팅 경로를 효율적으로 선정하는 DVS-PMIPMR (Differentiated Virtual Source-based Priority Minimum Interference Path Multicast Routing) 알고리즘을 제안한다. 마지막으로 같은 조건에서 더 많은 수의 멀티캐스트 라우팅 패스의 연결이 가능함을 시뮬레이션 및 성능분석 증명한다. Over the past decade, the improvement of communications technologies and the rapid spread of www (World Wide Web) have brought on the exponential growth of users using Internet and real time multimedia multicast services like video conferencing, tele-immersive virtual reality, and Internet games. The dense-wavelength division multiplexing (DWDM) networks have been widely accepted as a promising approach to meet the ever-increasing bandwidth demands of Internet users, especially in next generation Internet backbone networks for nation-wide or global coverage. A major challenge in the next generation Internet backbone networks based on DWDM technologies is the resolution of the multicasting RWA (Routing and Wavelength Assignment) problem; given a set of wavelengths in the DWDM network, we set up light-paths by routing and assigning a wavelength for each connection so that the multicast connections are set-upped as many as possible. Finding such optimal multicast connections has been proven to be Non-deterministic Polynomial-time-complete. In this paper, we suggest a new heuristic multicast routing and wavelength assignment method for multicast sessions called DVS-PMIPMR (Differentiated Virtual Source-based Priority Minimum Interference Path Multicast Routing algorithm). We measured the performance of the proposed algorithm in terms of number of wavelength and wavelength channel. The simulation results demonstrate that DVS-PMIPMR algorithm is superior to previous multicast routing algorithms.

Cascaded multiplexed optical link on a telecommunication network for frequency dissemination

We demonstrate a cascaded optical link for ultrastable frequency dissemination comprised of two compensated links of 150 km and a repeater station. Each link includes 114 km of Internet fiber simultaneously carrying data traffic through a dense wavelength division multiplexing technology, and passes through two routing centers of the telecommunication network. The optical reference signal is inserted in and extracted from the communication network using bidirectional optical add-drop multiplexers. The repeater station operates autonomously ensuring noise compensation on the two links and the ultra-stable signal optical regeneration. The compensated link shows a fractional frequency instability of 3 x 10(-15) at one second measurement time and 5 x 10(-20) at 20 hours. This work paves the way to a wide dissemination of ultra-stable optical clock signals between distant laboratories via the Internet network.

Reconfigurable asymmetric optical burst switching for concurrent DWDM multimode switching: architecture and research directions [Topics in Optical Communications

Dense wavelength-division multiplexing technology enables vast network capacity expansion over existing network infrastructure. Unfortunately, there is no single switching technology that can cost-effectively scale to a large number of DWDM channels while meeting the diverse needs of heterogeneous applications. For example, despite its rich set of traffic management capabilities, electronic packet switching requires hundreds of expensive optical/electrical/optical converter pairs just to terminate a single DWDM link. While optical switching technologies can bypass O/E/O conversion, neither of the two practical optical switching technologies, optical circuit switching or optical burst switching, can switch at the packet level. The proposed novel DWDM multimode switching router architecture allows electronic packet switching, optical circuit switching, and optical burst switching to be supported concurrently on an integrated router platform. In the proposed approach, the router supports a large number of DWDM channels cost effectively by maintaining a relatively small set of shared, though expensive, electronic switching ports. With this architecture, each DWDM channel can be individually reconfigured to a different switching mode, based on the dynamic traffic load. Individual applications, or individual types of messages within an application, can choose the mode that best suits its need.

Design procedures for backbone transport networks with shared protection: optimization-based models, exact and heuristic algorithms, and unavailability computations

This manuscript presents optimization-based design models and algorithms for reliable backbone transport networks. Due to their efficiency in providing data services and high data rates, dense wavelength division multiplexing (DWDM) networks became the technology of choice for these transport networks. DWDM networks achieve these high rates by enabling several wavelengths of light to be transmitted on a single strand of fiber. Optimization-based practical methods to design DWDM networks with both link-based and path-based shared protection schemes are introduced and compared in an empirical analysis. These design models address various restrictions inherent to DWDM technology including polarization mode dispersion and attenuation requirements. Furthermore, approximations are developed to determine unavailability for any given origin-destination pair in a DWDM network. Finally, path-based and link-based shared protection models are compared based on design costs and unavailability.

Contention avoidance and resolution schemes in bufferless all-optical packet-switched networks: a survey

Optical Packet Switching (OPS) is the promising switching technique to utilize the huge bandwidth offered by all-optical networks using the DWDM (Dense Wavelength Division Multiplexing) technology. However, optical packet contention is the major problem in an OPS network. Resolution and avoidance are two schemes to deal with the contention problem. A resolution scheme resolves collisions, while an avoidance scheme tries to reduce the number of potential collision events. Many OPS architectures rely on optical buffers to resolve contention. Unfortunately, optical buffering technology is still immature as it relies on bulky optical fiber delay lines. Furthermore, it requires a complex control. Therefore, a bufferless OPS network could still be the most straightforward implementation in the near future. In this article, we survey the contention resolution and avoidance schemes proposed for bufferless OPS networks. We also review the resolution and avoidance schemes that can handle the Quality of Service (QoS) issue in a QoS-capable bufferless OPS network.

Application of WDM holographic devices in access and metro networks

In this paper, a design of a generic multipurpose device is described. It can operate, in its basic structure, as a tunable wavelength filter, wavelength multiplexer or λ router; by using a more complex structure, the device works as an optical add drop multiplexer (OADM) or/and optical switch (OS). It can be used in both coarse and dense wavelength division multiplexing technology (CWDM/DWDM) according to the network application. Performance parameters of the device, like switching time, losses, crosstalk or polarization insensitivity are analyzed and compared with other switching technologies. Some applications of the holographic WDM multifunction device in METRO networks are described, such as the utilization of OADMs in optical path protection/reconfiguration between nodes (1 + 1 configuration) and the use of optical switches to interconnect nodes of the METRO–access network with the METRO-Core or long haul networks in a reconfigurable topology. Other applications in Access networks are possible, like the use of the OADMs in optical path protection between the optical line termination (OLT) at the central office (CO) and the remote node (RN) in a fiber to the office passive-optical network (FTTO-PON) or, in some specific cases, the utilization as tuneable holographic filters in a FTTO application, at the Business ONT (BONT), to select the assigned optical wavelength according to the services provided to the customer.

A multipurpose WDM holographic device for filtering, wavelength multiplexing and routing applications

This work describes the theory, design, and experimental results of a generic multipurpose device that can operate as a tunable wavelength filter, wavelength multiplexer and wavelength router. This device could be especially useful in optical networks applications based in both Coarse and Dense Wavelength Division Multiplexing technology (CWDM/DWDM). The enabling component is a Ferro-electric Liquid Crystal (FLC) Spatial Light Modulator (SLM) where dynamic holograms are implemented in real time. As a consequence, the device will be able to carry out different functions according to the hologram recorded on the SLM. The great advantage of this device is a polarization insensitivity operation, allowing low cross-talk and simple handling. Also some topics on Computer Generated Holograms (CGHs) design process are commented and general guidelines also are done. Laboratory experiments have demonstrated the capability of a phase FLC-SLM, with the great advantage of a polarization insensitivity operation, to diffract the incident light according its wavelength and hologram patterns, for the use in the former applications.

Design of a device with wavelength multiplexing and routing functions using dynamic holography on SLMs

This work describes the theory and design of a generic multipurpose device that can operate as a tunable wavelength filter, wavelength multiplexer and wavelength router. This device could be especially useful in optical network applications based in both coarse and dense wavelength division multiplexing technology. The enabling component is a ferroelectric liquid crystal spatial light modulator (SLM) where dynamic holograms are implemented in real time. As a consequence, the device will be able to carry out different functions according to the hologram recorded onto the SLM. The great advantage of this device is a polarization insensitivity operation, allowing low crosstalk and simple handling.

非圧縮スーパーハイビジョン信号の１６波高密度波長多重方式による長距離伝送

We describe an optical transmission system for uncompressed Super High-Vision (SHV), which is an extremely high resolution video system with 4000 scanning lines and 22.2 multi-channel audio. We transmitted an SHV signal composed of 16 HD-SDI signals a distance of 260 km through an existing optical fiber using four optical amplifiers and dense wavelength division multiplexing technology. Application of distributed Raman amplification to the system enabled the SHV signal to be transmitted up to 180 km without using optical relay amplifiers.

A Study of Waveband Assignment in Waveband Switching Optical Network

Tremendous internet traffic makes DWDM (Dense Wavelength Division Multiplexing) technology popularly applied in optical network and the scale of optical cross-connect (OXC) becomes larger. In order to save node cost and realize traffic grooming, waveband switching (WBS) with many new algorithms for lightpath establishment has been proposed. In this paper, the concept of RWA (routing and wavelength assignment) in wavelength-routed network is extended to RRA (routing and resource assignment) in hierarchical optical network. And a kind of resource assignment policy for RRA is proposed according to the path granularity. Then several new dynamic waveband assignment algorithms for sequential multi-granularity OXC (MG-OXC) in WBS network without wavelength converters are presented. They are SBP (shortest waveband path), FBP (first-fit waveband path), LBP (longest waveband path) and LBC (longest waveband combination) algorithms. Numerical results show that LBP algorithm is simple and more effective for middle-scale WBS optical network and LBC algorithm is suitable for large-scale one.

Next generation hierarchical CWDM/TDM-PON network with scalable bandwidth deliverability to the premises

Long haul optical networks have been on focus for more than two decades. With the advent of dense wavelength division multiplexing technology, optical long haul fiber networks have been so successful in delivering an unprecedented amount of bandwidth that they outperformed the traffic deliverability from/to the access network by orders of magnitude. The reason was a cost-efficiency mismatch; long haul ultra-high bandwidth networks can take advantage of state of the art and costly technology, which cost-sensitive access networks cannot. The result was an unbalanced traffic flow from/to access points to the network if one compares the aggregate flow of the long haul network with that of the access. Nevertheless, over the last decade technology at the access advanced and new standards have been developed so that in the access layer of the overall communications network the focus has shifted onto fiber optic access again. Thus, in the optical regime, two proposals have prevailed. One uses a time division multiplexing (TDM) scheme over a single wavelength and a comprehensive timing protocol, and the other uses coarse wavelength division multiplexing (CWDM) technology. Each technology has advantages and disadvantages, and the one attempts to address the disadvantages of the other. In this paper we describe a hierarchical CWDM/TDM passive optical network (PON). Our access network architecture is scalable, it is flexible to accommodate one of several topologies simultaneously, and it delivers any type of payload, synchronous and asynchronous that spans from DS0 to Gbps. We discuss the bandwidth flexibility, versatility, resiliency and cost efficiency of the access network. We also demonstrate that our network can deliver payload to more than 16,000 end-users using simple and existing optical technology. Thus, if one considers cost per bandwidth or per user, the cost-efficiency outperforms any previous PON access network. Moreover, we provide simulation results to support the viability of our network architecture.

Waveband switching in optical networks

The rapid advances in dense wavelength-division multiplexing technology with hundreds of wavelengths per fiber and worldwide fiber deployment have brought about a tremendous increase in the size (i.e., number of ports) of photonic cross-connects, as well as in the cost and difficulty associated with controlling such large cross-connects. Waveband switching (WBS) has attracted attention for its practical importance in reducing the port count, associated control complexity, and cost of photonic cross-connects. We show that WBS is different from traditional wavelength routing, and thus techniques developed for wavelength-routed networks (including, for example, those for traffic grooming) cannot be directly applied to effectively address WBS-related problems. We describe two multigranular OXC architectures for WBS. By using the multilayer MG-OXC in conjunction with intelligent WBS algorithms for both static and dynamic traffic, we show that one can achieve considerable savings in the port count. We also present various WBS schemes and lightpath grouping strategies, and discuss issues related to waveband conversion and failure recovery in WBS networks.

Optical networks and the future of broadband services

The evolution of broadband services will depend on the widespread deployment of optical networks. The deployment of such networks will, in turn, help drive increased demand for additional capacity. In this world, service providers will have a growing need to be able to flexibly adjust capacity to accommodate uncertain and growing demand. In this article, we present a cost model that highlights the advantages of new optical networking technologies such as Dense Wavelength Division Multiplexing (DWDM) over traditional architectures for optical networks. This analysis highlights the increased flexibility and scalability of DWDM networks, which lowers the deployment costs of such networks in light of growing and uncertain demand. The DWDM architecture holds the promise of allowing the emergence of wavelength markets, where traffic could be switched between service provider networks at the optical layer (without the need for multiple costly and wasteful electronic/optical conversions). While the DWDM and Optical Cross-Connect (OxC) technologies provide a technical infrastructure for supporting wavelength markets, additional developments are also likely to be required. This paper also considers some of the impediments to the growth of wavelength markets, namely, the need for secondary markets and standardized contracts.

Electrically Tunable Optical Fiber Mach-Zehnder Interferometer

An electrically tunable optical fibre Mach-Zehnder interferometer is reported, based on the magnetostrictive effect. The period and peak wavelength of the interference spectrum can be electrically tuned to match the International Telecommunication Union's standard wavelength grid and so it is promising to be used in dense wavelength division multiplexing technology.