Advantages of input wavelength conversion in optical packet switches

The objective of this study is to propose a new optical packet switching architecture in which the wavelength converters, needed to solve output packet contentions, are shared per input line; according to this sharing strategy the packets arriving at a given input fiber shares a converter pool that can be accessed when wavelength conversions are required. In the paper we evaluate the performances of the proposed architecture when control algorithms with different complexity, are adopted. Under a unicast traffic scenario the obtained performances are compared to the ones of the architectures in which the wavelength converters are shared per node and per output line respectively. The carried out comparison shows that, with respect to the architecture with wavelength converters shared per output line, the proposed architecture allows to obtain a 30% saving of wavelength converters when a simple control algorithm is adopted; the saving can reach 80% if an optimized control algorithm is used. On the contrary the architecture with sharing per node needs fewer wavelength converters than the proposed architecture, but has the drawback to have a switching matrix much complex evaluated in terms of needed number of semiconductor optical amplifier; this complexity is due to the flexibility provided to the arriving packets in accessing the converters bank shared per node.