Efficient path protection using bi-directional WDM transmission technology

Bi-directional WDM transmission is a technique that allows wavelengths to be transmitted simultaneously in both directions in a single fiber. Compared with unidirectional WDM systems, it not only saves the cost of deploying extra fibers, but also allows more flexible bandwidth provisioning. To exploit the advantages brought by this flexibility, we investigate path protection based on bi-directional WDM transmission system in this paper. With path protection, a call is accepted if and only if an active data path together with a disjointed backup path can be found in the network. With bi-directional WDM, backup resources sharing in both directions of a fiber is possible. To encourage resources sharing, new cost functions are judiciously designed. Based on them, two original path protection schemes are proposed in this paper, BiPro and BiProLP, where BiProLP aims at further economizing the hardware cost incurred by BiPro. In contrast to the traditional unidirectional schemes, we show that both BiPro and BiProLP can yield noticeably lower call blocking probability, higher system capacity and shorter active/backup path length