We consider a traffic-groomed optical network consisting of N nodes arranged in tandem. This optical network is modeled by a tandem queueing network of multi-rate loss queues with simultaneous resource possession. Two approximation methods are proposed for the analysis of this queueing network assuming that the total number of servers in each multi-rate loss queue is very large. The accuracy of these two approximation methods as well as the accuracy of the familiar link independence algorithm is verified by simulation. As an additional contribution, the simulation estimates have been obtained using adaptive rareevent simulation techniques based on importance sampling. This is because call blocking probabilities tend to be very small and it is not feasible to estimate them using standard simulation techniques © 2005 IEEE.