Hybrid wavelength hopping/time spreading schemes for use in massive optical networks with increased security

Analysis of hybrid wavelength hopping/time spreading systems and their classification into symmetric and asymmetric systems (undercolored and overcolored asymmetric systems) is given. The characteristics of a hybrid system using extended quadratic congruence sequences for spreading and prime sequences and their cyclic shifts for hopping are examined. It is shown that the sequences exhibit excellent cross-correlation properties even in the case of a general asymmetric overcolored system. Analysis of the security properties of hybrid systems is presented both from the viewpoint of exhaustive search and from the viewpoint of chosen attack. Initial investigations indicate that the system can be so configured to allow high level of protection against determined attack, with this being especially true for an asymmetric system. Because of the massive number of users the system can support, the proposed scheme is suitable for large optical LAN´s with increased security demands