Fault Management in Transparent Optical Networks

Fault Management in Transparent Optical Networks

Carmen Mas Machuca (Technische Universität München, Germany)
DOI: 10.4018/978-1-61350-426-0.ch004
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The advantages of transparent optical networks such as high capacity and low cost can be outweighed by their complex fault management and the high impact of the faults occurring within them. Indeed, transparent optical networks reduce unnecessary, complex, and expensive opto-electronic conversion, to the cost of having faults more deleterious and affecting longer distances than in opaque networks. Moreover, transparent optical networks have limited monitoring capabilities, which could hinder efficient and accurate fault detection and localization. Different approaches have been proposed in the literature to perform fault localization, targeting different fault scenarios (e.g. single/multiple faults or looking at the optical/higher layers), and considering different assumptions (e.g. ideal/existence of false or lost alarms). Furthermore, fault management depends on the placement of monitoring equipment, whose optimization has been studied and also presented in this chapter.
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Transparent Optical Networks

A fault can be defined as the unexpected interruption of component function. Two types of faults can be distinguished: Soft faults are the faults causing degradations of the signal quality and may occur due to aging, misalignments or non-ideal environment conditions (temperature, humidity, etc.), whereas hard faults are the faults causing a complete signal interruption such as fiber cut. Based on statistics given by Grover (2004), faults at the nodes are rarer than faults at the links. Most of the hard faults of links are due to digs-up, whereas most of the soft faults of links are due to material degradation to undesired environmental conditions.

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