In this paper, we present a heuristic algorithm for effectively assigning a limited number of wavelengths among the access stations of a multihop network wherein the physical medium consists of optical fiber segments which interconnect wavelength-seleetive optical switches. Such a physical medium permits the limited number of wavelengths to be re-used among the various fiber links, thereby offering very high aggregate capacity. Although the optical connectivity among the access station can be altered by changing the states of the various optical switches, the resulting optical connectivity pattern is constrained by the limitation imposed at the physical level. We also study two routing schemes, used to route requests for virtual connections.
The heuristic is tested on a realistic traffic model, and the call blocking performance of new requests for virtual connections is studied through extensive simulations and compared against the blocking performance of an ideal infinite capacity centralized switch (lowest possible call blocking caused exclusively by congestion on the finite capacity user input/output links, never by the switch fabric itself). Surprisingly, we find that, for a wide range of parametem, the blocking performance of the Iightwave network is almost the same as that of the ideal centralized switch. From these results, we conclude that the heuristic algorithm is effective and the routing scheme is efficient. ?vlanuwrip( recei~cd March 7, 1994; rcvistxl June 13, 1994; approved by [hc IEEEIACM TRANSAmONS m NI I'WORKING Editur R. Ramaswami. This work was supp~mcd by ARPA under Contract MDA972-92-H-001(). Z. Zhwrg IS with AT&T Bell Labma[uries, Middletmvrr, NJ 07748 USA (c-mail: ~hang~'mrsp(~ck. mt,att.c(lm).