Since the deployment of optical communications networks, carriers have used many mechanisms to protect fiber in the core, because of the large volume of traffic carried in the core, and the affect of a failure on the entire user community. Access links, connecting end users to the core network were not protected because they affected a small number of customers, carried relatively low bandwidth traffic and were less critical. As enterprises use ever growing bandwidth and become increasingly dependent on their network connectivity, they demand protected services. Since fiber breaks can occur anywhere in the network, including the so-called "last mile" carriers are looking today for protection systems for the access and edge network links. This paper focuses on the emerging solutions for this application, detailing the key criteria for selecting fiber protection switches: optical performance and cost effectiveness (important because the cost must be amortized over a small number of customers). It discusses
solutions to the various access network topologies and common protection schemes.
Since the deployment of optical communications networks, carriers have used many mechanisms to protect fiber in the core, because of the large volume of traffic carried in the core, and the affect of a failure on the entire user community. Access links, connecting end users to the core network were not protected because they affected a small number of customers, carried relatively low bandwidth traffic and were less critical. As enterprises use ever growing bandwidth and become increasingly dependent on their network connectivity, they demand protected services. Since fiber breaks can occur anywhere in the network, including the so-called "last mile" carriers are looking today for protection systems for the access and edge network links. This paper focuses on the emerging solutions for this application, detailing the key criteria for selecting fiber protection switches: optical performance and cost effectiveness (important because the cost must be amortized over a small number of customers). It discusses solutions to the various access network topologies and common protection schemes.
PONs are gaining popularity in areas with high population density. Extensive deployment of fiber plant, along with the introduction of cost effective network devices promise ample of affordable bandwidth to the home and the premise. The distribution network is typically organized as tree architecture and utilizes simple optical splitters. The use of fixed splitters results, however, in a rigid topology, incapable of changes or expansion to meet the needs of demographic changes. A new breed of splitters, based on Planar Lightwave Circuit (PLC) technology, allows service providers to programmatically change the split rations. This feature facilitates a phased build-out of the PON network or changes to the network topology. This article describes the underlying technology for these programmable splitters and explains how they can add flexibility to PON networks.
Evolving carrier networks are starting to include optical networking, but current optical elements form islands of communications, not the utopian “global intelligent optical network” that is the end goal. Although dense wavelength division multiplexer (DWDM) technology leverages the cost and availability of fiber, each wavelength in DWDM links needs its own transponder, an expensive O-E-O (opto-electrical-opto) device in which optical signals are converted back to their electrical (binary) format to process the information. In today’s carrier networks, O-E-O is needed to terminate each optical end point in order to deliver it in its correct format to the specific addressees using high-level format-dependent protocols. The presentation will discuss how 60-80% of all traffic that passes through an O-E-O switch at midpoints in a network typically does not require processing at those points and, in fact, get re-converted and re-transmitted. The equipment that does this costs millions of dollars; takes up more space; uses a lot of power (expense and heat); and creates additional opportunities for network failures. Adding O-O-O (photonic, or all–optical) switches to the architecture as needed allows higher speeds, less real estate, lower capital and operational expenditures, improved network reliability, and better customer response.
While most OADM systems deployed today are static, carriers offering new wavelength services, are looking for ways to migrate towards reconfigurable OADM and dynamically reconfigurable OADM. ROADMs allow carriers to automate service provisioning, wavelength management and failsafe mechanisms, thereby eliminating slow, costly and error-prone manual network configuration. And although next-generation systems offer this flexibility as an integral part of their architecture, carriers must protect their existing investment, extending the life of their existing networks. This article examines the use of add-on optical switching systems, as a cost- and time-effective means for upgrading legacy networks. Two examples are given. In the first, a static OADM is upgraded into a reconfigurable system. The second example shows how existing OADM systems can be upgraded to support dynamic reconfigurability. The article examines also particular advantages of Planar Lightwave Circuits (PLC) for these applications.
The mission-critical nature of high-speed networks imposes stringent requirements for high availability. Resilience is achieved through highly reliable network nodes, and through network protection / restoration mechanisms that rely on various forms of redundancy and fault tolerance. Although data networks can be restored at the IP layer, carriers and enterprises alike, are increasingly relying on protection at the physical layer, to achieve fast and reliable recovery. Faulty network components (nodes or links) are quickly identified and restoration takes place by automatically bypassing them or replacing them with spares. Switchover from a failed component to a spare is called "Protection Switching’. 1:N protection switching, in which a single spare is used to protect several (N) components, was found to be most cost-effective. Furthermore, operational expenses of fiber-based (optical) networks can be minimized through the use of all-optical switches that are transparent to data rates and protocols, allowing easy network upgrades. This article discusses issues associated with optical equipment protection switching and describes a new breed of intelligent protection systems, based on Planar Lightwave Circuit (PLC) technology.
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