Bi-link-failure-free Routing and Wavelength Assignment for torus-based avionic WDM LANs

In this paper, we focus on exploring the fault tolerance potential of the torus topology in designing the next-generation avionic onboard backbone communication systems that apply optical Wavelength Division Multiplexing (WDM) technologies. The exemplifying study is specifically given to a 4×4 torus structure in which all backbone node pairs´ communications are enabled in a simultaneous fashion. We propose an optimal Spare Routing and Wavelength Assignment (SRWA) scheme, which makes the network able to tolerate an arbitrary bidirectional link (bilink) failure without loss of connections. This SRWA scheme is at a cost of spare wavelengths equivalent to 25% of wavelengths required for working lightpaths, which results from an optimal Working lightpaths Routing and Wavelength Assignment (WRWA) scheme. In addition, for the purpose of maximizing spare resource utilization, an enhanced 4-way protection scheme is introduced to further improve the protection of connections beyond the first bilink failure via exploiting the remaining capacity in the set of spare resources. The simulation results validate the proposed SRWA design and also show evident reliability benefits from applying the enhanced 4-way protection scheme.