In this paper, we investigate the capital and operational expenditures for two next generation optical access
(NGOA) networks based on wavelength division multiplexing (WDM) technology in dense urban areas. It is shown that
with a proper fiber layout design, minor extra investment for protection of NGOA networks can make a significant
saving on failure related operational cost.
This paper presents a comprehensive cost model for migration towards FTTH, some case study results from different
network area scenarios, as well as the identification of the most important cost factors to be considered by operators
aiming at increasing the profitability of their networks.
Network security is becoming a very sensitive and important topic for equipment manufacturers and network operators. In transparent optical networks, security is even more complex since the optical signals are not regenerated as in opaque networks and, therefore, the faults and attacks at the physical layer are more difficult to detect and isolate without significantly affecting the overall network performance. In this paper we define Failure Management as the prevention, detection, and reaction against failures. Failures are defined as the interruptions of the normal functioning of the network and comprise faults (accidental interruptions) as well as attacks (intentional interruptions which can be performed by service disruption or eavesdropping). Our work deals with a solution to detection of failures in transparent networks. For this purpose we have extended a Fault Location algorithm developed for opaque optical networks to be used in transparent networks and be able to also locate attacks. The proposed algorithm is called Transparent Failure Location Algorithm (TFLA). The first part of the extension is based on the study of other optical network elements such as Optical Add/Drop Multiplexers (OADMs), Optical Cross-Connects (OXCs), wavelength converters, Optical Line Terminators, etc. The vulnerability of these elements depends on their architecture and/or fabrication technology and, therefore, different attacks can be considered. A classification of these components based on the masking and alarming properties is proposed. The second part of the extension is based on the monitoring equipment that may be available in transparent networks. The TFLA was applied for the case of a transparent ring of the Pan-European network.
A single failure in a communication network may trigger many alarms. When the communication network uses optical fibers as a transmission medium and increases its capacity by using Wavelength Division Multiplexing and Space Division Multiplexing, the number of alarms and the difficulty to locate the failure are considerably higher. In this case, a single failure may interrupt several channels so that the quality of lost information is larger. We propose an alarm filtering algorithm for the fault management of an optical network that supports multiple failures and works in the presence of passive elements, that is, network elements which may fail but never generate an alarm (e.g. optical fibers). Our algorithm avoids the use of failure probabilities because they are difficult to estimate and it does not need a global knowledge of the network topology. Moreover it also tolerates alarm losses. The algorithm results in the presentation to the human manager of a list of faults which may have caused the observed alarms. The alarm filtering problem is defined and formalized at the level of abstraction for devising the Alarm Filtering Algorithm. The algorithm is then applied to the optical network of the ACTS COBNET project.
Conference Committee Involvement (1)
Network Architectures, Management, and Applications
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