This paper considers optical networks which employ w avelength-routing switches that e n able the e stablishment o f w avelength-division-multiplexed (WDM) channels, called lightpaths, between node-pairs. In such n etworks, the failure of a single link may cause the failure of several optical channels. Given a set of lightpaths, that m ay comprise of a virtual topology, a n d xed alternate r o u ting t ables at each node, this paper examines the f o l l o wing problem: how t o a l l o c a te

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... acity i n a n o ptimal fashion and assign routes and w avelengths to e a c h lightpath s u ch t hat u p o n a n y link failure lightpaths that are affected by t he failure, can be reestablished without a n y blocking. A simple approach, called one-on-one protection, protects against link failures by reserving a link-disjoint backup lightpath for every working lightpath. In this paper, we examine a n I n teger Programming ( I P ) a p proach, called multiplexed s p are capacity protection, t hat m ultiplexes the spare capacity a m o n g all lightpaths in an optimal fashion. This paper examines the performance of this approach on representative n etwork t opologies, and s h ows that this approach is superior to o n e-on-one protection.