A WDM Cross-Connected Star Topology for Multihop Lightwave Networks

In this paper, we propose a star topology for multihop lightwave networks in which the conventional N x N passive star coupler is replaced by Axed wavelength division multiplexed (WDM) cross connects. The proposed topology overcomes three major limitations of the conventional star topology. First, it reduces the number of wavelengths needed in a (p, k) ShuffleNet from kpk + 1 wavelengths in the conventional topology to p wavelengths in the proposed one. Second, the signal power loss due to the 1/N power splitting at the star coupler no longer exists in the WDM cross connects and, therefore, the restriction on the supported number of users by the star network is alleviated. Third, it completely eliminates the need for wavelength filtering at the input to the receivers as is the case in the conventional star topology. The use of 2 x 2 WDM lapped couplers as a cheap WDM cross connect for a (2, k) ShuffleNet is investigated. We also find that a p x p star coupler followed by p fiber Fabry-Perot filters can be used as a p x p WDM crossconnect for a (p, k) ShuffleNet at the expense of using p2 rather than p wavelengths.