The development of the photonic technologies enabled high transfer over optical fibers. The key technology for this development is WDM which enables hundreds of wavelength channels which transfer data in Gb/s speeds to be multiplexed in one signal suitable for transfer over the optical fiber. As a result of huge quantity of the transferred data, network failures can cause big financial losses as well as the reputation of the service provider. For that reason the application of the different protection methods in the WDM ring structure enables network operators to even in the circumstances of failure (i.e. cable cut off) provide to its users normal performance or in other words quality service. Service Quality requests are usually defined by a contract (SLA- Service Level Agreement) between the operators and its users as well as the penalties which need to be paid by the operator in cases when the quality is not on the level which was defined in the SLA contract. Surveillance of the service is generally introduced over connection availability which is a probability that the connection will be correct in some moment in time. The availability of the connection depends of the availability of the network components alongside (optical fibers, optical add/drop multiplexors and switches...). In order to provide quality service to its users introduced over availability and defined by the SLA contract, operators apply different protection methods. In this paper we shall focus on the protection of the wavelength channel in the ring WDM network.
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