Development of monitoring system for FTTH‐PON using combined ACS and SANTAD

This paper proposes a design of Access Control System (ACS) for fiber‐to‐the‐home passive optical network (FTTH‐PON). Our design works on a standard local area network using a specially designed hardware interfaced with a microcontroller integrated Ethernet to monitor the status of optical signals flow and provides the restoration against fiber failures/faults in FTTH‐PON. We also introduce the centralized troubleshooting system by means of Smart Access Network Testing, Analyzing, and Database (SANTAD). ACS is the subsystem that controls the troubleshooting mechanism carried out by SANTAD. This design will be implemented together with optical line terminal (OLT) at central office (CO) to centralized monitoring and for controlling each optical fiber line's status as well as detecting any failure that occurs in the network system downwardly from CO toward multiple optical network units at different customer residential locations. The scope of this discussion highlighted only the monitoring and controlling instead of the restoration scheme offered. Copyright © 2009 John Wiley & Sons, Ltd.     

Protection switching and local area network emulation in passive optical networks

This paper proposes and experimentally demonstrates an automatic-protection-switching (APS) mechanism against distribution fiber breaks in passive optical networks (PONs). The protection of optical-network units (ONUs) that are located at the customer premises is carried out by monitoring the distribution fiber using the traffic that is transported among the customers in the PON. This configuration emulates a local area network (LAN) over the existing PON while facilitating the switching of signal transmissions to a predetermined protection path in an event of a distribution fiber break. As failure detection and APS are performed independently by each ONU in a distributed manner, the processing complexities and delays are reduced at the central office (CO). The restoration of the traffic transported between the CO and an ONU in the event of the distribution fiber break is performed by interconnecting adjacent ONUs and carrying out signal transmissions via an independent but interconnected ONU. Such a protection mechanism enables multiple adjacent ONUs to be simultaneously protected by a single ONU utilizing its maximum available bandwidth. This paper experimentally verifies the feasibility of the proposed protection mechanism in conjunction with two different LAN-emulation schemes with a 1.25-Gb/s upstream baseband transmission to the CO and a 155-Mb/s LAN data transmission on a radio-frequency carrier. The experimental results obtained from both schemes are compared, and the power budgets are calculated to analyze the scalability of each scheme.     

Experimental demonstration of CW light injection effect in upstream traffic TDM-PON

High capacity time-division-multiplexed passive optical network (TDM-PON) is an emerging fiber access network that deploys optical access lines between a carrier’s central office (CO) and a customer sites. In this investigation, we demonstrate and analyze the continuous wave (CW) upstream effect in TDM-PONs. Besides, we also propose and design a protection apparatus in each optical network unit (ONU) to avoid a CW upstream traffic in TDM-PONs due to sudden external environment change or ONU failure. When an upstream CW injection occurs in TDM access network, the protection scheme can stop the CW effect within a few ms to maintain the entire data traffic.     

Novel schemes for local area network emulation in passive optical networks with RF subcarrier multiplexed customer traffic

This paper proposes two novel optical layer schemes for intercommunication between customers in a passive optical network (PON). The proposed schemes use radio frequency (RF) subcarrier multiplexed transmission for intercommunication between customers in conjunction with upstream access to the central office (CO) at baseband. One scheme employs a narrowband fiber Bragg grating (FBG) placed close to the star coupler in the feeder fiber of the PON, while the other uses an additional short-length distribution fiber from the star coupler to each customer unit for the redirection of customer traffic. In both schemes, only one optical transmitter is required at each optical network unit (ONU) for the transmission of customer traffic and upstream access traffic. Moreover, downstream bandwidth is not consumed by customer traffic unlike in previously reported techniques. The authors experimentally verify the feasibility of both schemes with 1.25 Gb/s upstream baseband transmission to the CO and 155 Mb/s customer data transmission on the RF carrier. The experimental results obtained from both schemes are compared, and the power budgets are calculated to analyze the scalability of each scheme. Further, the proposed schemes were discussed in terms of upgradability of the transmission bit rates for the upstream access traffic, bandwidth requirements at the customer premises, dispersion tolerance, and stability issues for the practical implementations of the network.     

光纤自动切换保护系统的应用探讨

分析光纤自动切换保护系统的原理,以我公司为例,在光传输网络主要路由上,接入光纤自动切换保护器,利用保护器构建出光纤保护网络,当被保护的光纤发生故障中断或者衰耗增大导致通信传输质量下降时,光纤线路自动切换保护技术却能使网络进行实际切换,用恢复机制作为第二道防线对付网络范围的故障和失效,恢复通信的畅通,从而增强了我公司通信网络的可靠性。     

Optical cross-connect system in broad-band networks: system conceptand demonstrators description

A network robust to future evolution in network topologies or transmission formats and bit rates, which would be achieved by introducing an all-optical transparent layer in the transport network hierarchy is considered. The transparency would permit use of physically common fiber lines and nodes for different transmission hierarchies and/or formats. A transparent network could be achieved by combining photonic switching with electronic switching technology in the network nodes. A combination of wavelength routing and space-division switching in the optical layer would increase the capacity, as well as the flexibility in a network, allowing routing with higher granularity within the optical layer. Two optical cross-connect demonstrators have been set up. One demonstrates protection switching and restoration of traffic in a future transport network, and the other demonstrates routing of subscriber signals to different service switches in a local exchange. Space switches, tunable lasers and filters are the key technologies used to obtain enhanced flexibility     

智能多粒度光交叉连接节点的设计与实现

提出了一种新型多粒度光交叉连接(MG-OXC)的体系结构,它可以完成光纤、波带、波长的交换,以及不同粒度业务的上下话路.同时介绍了由三个真实多粒度光交叉连接节点与若干虚拟光节点所组成的智能多粒度光网络试验平台的设计与实现.实验平台支持动态的可配置的网络拓扑、自动的邻居发现、受限的波长、波带路由,以及光层快速的保护与恢复.     

Strategy for protection and restoration of optical paths in WDM backbone networks for next-generation Internet infrastructures

This paper proposes and analyzes a strategy for protection and restoration of optical paths in wavelength division multiplexing (WDM) networks for next-generation Internet infrastructure. Assuming a network model in which a multiprotocol label switching (MPLS) layer is overlaid on top of a WDM layer, and a segregation of the traffic on a wavelength basis, the strategy is based on a network dimensioning aiming at: 1) the support of different types of traffic, relating to different service categories; 2) the guarantee that all the wavelength paths carrying mission-critical services (with stringent quality of service requirements) are protected against failure; and 3) the possibility of restoring a large amount of wavelength paths carrying Internet best-effort services, i.e., low-priority (LP) preemptible traffic with no QoS requirements. The reference network scenario is an overlay model in which the optical network interacts with an MPLS network with a separated control plane; the optical network manages its resources to better serve the traffic coming from the MPLS network. Two path protection schemes, namely, disjoint path (DP) and single-link basis (SLB), and a link protection mechanism, namely, local repair (LP), are investigated. Furthermore, the paper considers both the case of using wavelength conversion in the optical nodes and the case in which wavelength conversion is not used at all. The analysis compares the performance of the different strategies in terms of the percentage of optical paths carrying LP traffic not served by the optical network after a failure and of the dimensions of the optical nodes for all the schemes. The analysis reveals that the proposed approach allows the restoration of a large amount of best-effort traffic with a reasonable increase of network redundancy.     

OTN保护方式及多重保护协同方案

目前OTN是业务承载的主要方式,为提高网络的安全性,网络中采用OLP/OMSP、ODUk SNCP 1+1、OCP 1+1等多种保护措施.同时,业务层自身也有保护,多重保护嵌套后,如何实现各种保护的协调,保证故障时不会出现多保护同时倒换,避免倒换震荡和业务闪断是需要在网络开通时需要关注的问题.本文通过分析不同保护方式倒...     

Survivable WDM mesh networks

In a wavelength-division-multiplexing (WDM) optical network, the failure of network elements (e.g., fiber links and cross connects) may cause the failure of several optical channels, thereby leading to large data losses. This study examines different approaches to protect a mesh-based WDM optical network from such failures. These approaches are based on two survivability paradigms: 1) path protection/restoration and 2) link protection/restoration. The study examines the wavelength capacity requirements, and routing and wavelength assignment of primary and backup paths for path and link protection and proposes distributed protocols for path and link restoration. The study also examines the protection-switching time and the restoration time for each of these schemes, and the susceptibility of these schemes to multiple link failures. The numerical results obtained for a representative network topology with random traffic demands demonstrate that there is a tradeoff between the capacity utilization and the susceptibility to multiple link failures. We find that, on one hand, path protection provides significant capacity savings over link protection, and shared protection provides significant savings over dedicated protection; while on the other hand, path protection is more susceptible to multiple link failures than link protection, and shared protection is more susceptible to multiple link failures than dedicated protection. We formulate a model of protection-switching times for the different protection schemes based on a fully distributed control network. We propose distributed control protocols for path and link restoration. Numerical results obtained by simulating these protocols indicate that, for a representative network topology, path restoration has a better restoration efficiency than link restoration, and link restoration has a faster restoration time compared with path restoration.     

A broadcast-and-select OADM optical network with dedicated optical-channel protection

A metro-area optical-ring network based on a novel optical add-drop multiplexer (OADM) architecture using a wavelength blocker is proposed. We demonstrate experimentally the performance of the OADM and capability of optical channel dedicated protection in a two-fiber ring network with 24/spl times/10 Gb/s dense wavelength division multiplexing traffic capacity. The channel-by-channel optical protection of the network is enabled by using a liquid crystal-based wavelength-selective switch as the protection switch and erbium-doped fiber amplifiers (EDFAs) with fast transient-gain control. The bit-error rate performance of the network is studied for the normal operation and for the transition to the protection state from a failure. The network protection for all channels is provided within 5 ms on a cable-cut failure. Importance of transient-gain control during protection switching to reduce the network transients is also discussed.     

市县传输网光线路保护系统的设计和应用

本文首先介绍了某地级市有线市县传输网的拓扑结构和业务类型,然后阐述了光线路保护系统的组成和原理,最后提出了市县传输网光线路保护的设计方案。该方案从光缆长度估算、光功率调整、色散补偿计算等方面入手,详细论述了三个方面的设计方法。     

5G时代,有线接入网基础资源布局思路探讨

双千兆时代,网络规模空前巨大,有线接入网更是因覆盖范围广,建设规模大,投入人力多,投资占比高等因素,成为研究重点。文章根据有线接入网架构演进,从“点(各类业务及分纤点)、线(各级管线)、面(业务汇聚区)”三个层面对基站、家客、集客等业务接入、分纤点规划及业务汇聚机房等基础资源规划进行研究。     

Toward efficient failure management for reliable transparent optical networks - [Topics in optical communications]

Security and reliability issues are of utmost importance in transparent optical networks due to the extremely large fiber throughput. Fast and successful reaction and restoration mechanisms performed by failure management can prevent loss of large amounts of critical data, which can cause severe service disruption. In this article we discuss failure management issues in TONs, the mechanisms involved, and optical monitoring techniques. Furthermore, we propose applying structural properties of self-organizing systems to create a "small world" hybrid supervisory plane that can enable faster system-wide communication. We also investigate the possibility of a scale-free structure aimed at improving robustness in the network and propose various topology generation algorithms.     

The TPC-5 Cable Network

The TPC-5 Cable Network (TPC-5 CN) will be the first self-healing trans-Pacific ring network. It consists of a ring of undersea cables connecting six network nodes at six cable landing sites. The TPC-5 CN brings together a unique blend of technology to achieve the architectural robustness and transmission performance needed by network users. Among the technologies used in the TPC-5 CN are erbium doped fiber optical amplifiers (EDFAs), 5 Gb/s line terminating equipment (LTE), line monitoring equipment (LME), synchronous digital hierarchy (SDH) STM-16 add/drop multiplexers (ADMs) with four-fiber-ring automatic protection switching capability, and network management equipment (NME). The article describes the operation of each of these technology and how this equipment is collectively integrated to achieve the performance and functionality of the TPC-5 CN     

Protection cycles in mesh WDM networks

A fault recovery system that is fast and reliable is essential to today's networks, as it can be used to minimize the impact of the fault on the operation of the network and the services it provides. This paper proposes a methodology for performing automatic protection switching (APS) in optical networks with arbitrary mesh topologies in order to protect the network from fiber link failures. All fiber links interconnecting the optical switches are assumed to be bidirectional. In the scenario considered, the layout of the protection fibers and the setup of the protection switches is implemented in nonreal time, during the setup of the network. When a fiber link fails, the connections that use that link are automatically restored and their signals are routed to their original destination using the protection fibers and protection switches. The protection process proposed is fast, distributed, and autonomous. It restores the network in real time, without relying on a central manager or a centralized database. It is also independent of the topology and the connection state of the network at the time of the failure.     

A next-generation optical regional access network

We describe an optical regional access network which combines electronic IP routing with intelligent networking functionality of the optical WDM layer. The optical WDM layer provides such networking functions as network logical topology reconfiguration, optical flow switching to offload traffic and bypass IP routers, wavelength routing of signals, protection switching and restoration in the optical domain, and flexible network service provisioning by reconfigurable wavelength connectivity. We discuss key enabling technologies for the WDM layer and describe their limitations. The symbiosis of electronic and optical WDM networking functions also allows support for heterogeneous format traffic and will enable efficient gigabit-per-second user access in next-generation Internet networks     

Invited: Routing Strategies for Capacity-Efficient and Fast-Restorable Mesh Optical Networks

Wavelength division multiplexed (WDM)-based mesh network infrastructures that route optical connections using intelligent optical cross-connects (OXCs) are emerging as the technology of choice to implement the next generation core optical networks. In these architectures a single OXC is capable of switching tens of terabits of traffic per second. With such data transfer rates at stake, it becomes increasingly challenging for carriers to (1) efficiently and cost-effectively operate and manage their infrastructure, and (2) cope with network failures while guaranteeing prescribed service level agreements (SLAs) to their customers. Proper routing of primary and backup paths is a critical component of the routing and restoration architecture required to meeting these challenges. In this paper we review some of the various strategies and approaches proposed so far to intelligently route connections while at the same time providing guaranteed protection against various types of network failures. We explore the tradeoffs associated with these approaches, and investigate in particular different, sometimes competing aspects, such as cost/capacity required, level of protection (link vs. node failure), restoration time, and complexity of route computation.     

A resilient star-ring optical broadcast-and-select network with a centralized multi-carrier light source

This article presents a resilient star-ring optical broadcast-and-select network with a centralized multi-carrier light source (C-MCLS). It consists of a star part network and a ring part network. Optical carriers generated by the C-MCLS are broadcast to all network nodes, which select and utilize them for data transmission. Optical carrier distribution as well as data transmission and receiving are performed in the star part network. The ring part network is for fiber failure recovery. The network resilience property enables the design of a fast distributed failure recovery scheme to deal with single and multiple fiber failures. We introduce a fiber connection automatic protection switching (FC-APS) architecture that only consists of optical couplers and 1 × 2 optical switches for each network node. Based on the FC-APS architecture, we design a distributed failure recovery scheme to recover the carriers and data affected by fiber failures. The fiber failure detection and failure recovery operations are performed by each network node independently only using its local information. We evaluate the recovery time of the distributed failure recovery scheme compared with that of the centralized one. Numerical results show that the distributed scheme greatly reduces the recovery time compared to the centralized configuration in the recoveries of both single and multiple fiber failures. Optical power loss analysis and compensation of the recovery routes in the distributed scheme are also presented. We show the required number of optical amplifiers for the longest recovery route in the distributed scheme under different numbers of network nodes and fiber span lengths.     

All-optical four-fiber bidirectional line-switched ring

An all-optical four-fiber bidirectional line-switched ring (O-4F/BLSR) architecture is proposed. This new physical layer networking protocol uses wavelengths as tributaries and an optical supervisory channel to carry overhead information. Optical channels can be added and dropped from the ring, and virtual wavelength paths can be provisioned. Both node and link failures of a network can be protected through a two layer protection scheme. Protection switching within the optical multiplex section layer (OMS) restores failure caused by loss of optical continuity in a way similar to the SONET 4F/BLSR line switching. Protection switching within the optical channel layer restores single channel failure using 1:N protection. Test results show that the O-4F/BLSR can restore traffic in less than 50 ms. A self-healing, bandwidth efficient, and scalable all-optical transport network evolving from this O-4F/BLSR architecture is possible