Thus a physical fiber infrastructure can be broken into a logical wavelength topology with more flexibility and finer granularity. Thus wavelength conflicts can occur if two signals with identical wavelengths need to be transmitted over the same fiber. This results in restrictions in the possible network configurations and an associated increased complexity in the planning of the network topology. All processing occurs in the optical domain by means of advanced optical components. All-optical wavelength converting components have been a research topic for many years, but have not had any market impact so far.
Transponders convert any input signal to an output signal with a well-defined wavelength.
This increases the cost of the network, because transponders are relatively expensive. If some risk for wavelength collisions is acceptable, it is possible to use a reduced configuration where transponders are used for only some of the channels. This solution should be cost-effective compared with the solutions already listed, because there is no need for wavelength interchanging devices at each node in the network. Also, it requires the use of centralized information about the entire network configuration and therefore increases the complexity of logistic challenges related to provisioning and spare parts. This solution is therefore more appropriate for static networks than for more-dynamic networks.