Found That Almost All of the Network Performance Im- Provement Ooered by an Ideal, Full-range Wavelength Translator Can Be Gained from a Translator with Only Half of the Full Translation Range

Acknowledgments The authors wish to thank Steve Madden from Tel-stra Research Laboratories and Rod Tucker from The University of Melbourne for helpful discussions. Jen-nifer Yates also thanks Telstra Research Laboratories for nancial support.sensitive Wavelength Conversion of 10Gbit/s Signals with SOAs in a Michelson interferometer," Electron. Figure 7: Blocking probability versus ooered traac for diiering degrees of wavelength translation in a 6-node unidirectional ring with 10 wavelengths. small improvement previously observed with the introduction of wavelength translation: for a total ooered network traac of 6.0 Erlangs, the observed blocking probability is 4:6 10 ?3 with no translation, and improves slightly to 1:9 10 ?3 if full-range translation is allowed. However, Figure 7 also shows that a significant proportion of this improvement in network performance is obtained with limited-range translation. For instance, for a total ooered network traac of 6.0 Erlangs, the blocking probability is 2:110 ?3 if translation by 44% of the full range is allowed. Figure 7 is signiicant because it suggests that limited-range wavelength translation is useful even when wavelengths are not assigned randomly. In contrast with the analytical results presented in Section 3.2, the unidirectional ring simulations used to generate Figure 7 performed non-random assignment of wavelengths, and assigned wavelengths on multiple links simultaneously. However, Figure 7 shows that, despite these diierences between the multiple-hop paths of Section 3.2 and the unidirectional ring, in both cases limited-range wavelength translation can give useful improvements in network performance. Compared with the ring network, a mesh-torus topology using the routing algorithm speciied in 6] has few paths which utilise common adjacent links. Consequently, the introduction of wavelength translators into a mesh-torus network will produce more signiicant improvements in the blocking probabilities than in a unidirectional ring 6]. Blocking probabilities for diierent degrees of wavelength translation in an 11 11 mesh-torus topology with ve wavelengths are plotted against ooered traac in Figure 8. Limited translation is again shown to provide a signiicant proportion of the performance improvement introduced by full-range translation. For instance, for a total network ooered traac of 60 Erlangs, the observed blocking probability is 0.025 with no translation and 0.003 with full-range translation. With limited-range translation by 25% of the full range, the blocking probability is 0.0045. If the degree of translation is increased to 50% of the full range, the blocking probability is further reduced to only 0.0035. Therefore, once again, very limited translation provides considerable network performance …