Approximation algorithms for wavelength assignment

Winkler and Zhang introduced the FIBER MINIMIZATION problem in [10]. They showed that the problem is NP-complete but left the question of approximation algorithms open. We give a simple 2-approximation algorithm for this problem. We also show how ideas from the Dynamic Storage Allocation algorithm of Buchsbaum et al. [4] can be used to give an approximation ratio arbitrarily close to 1 provided the problem instance satisfies certain criteria. We also show that these criteria are necessary to obtain an approximation scheme. Our 2-approximation algorithm achieves its guarantee unconditionally. We also consider the extension of the problem to a ring network and give a 2+o(1)-approximation algorithm for this topology. Our techniques also yield a factor-2 approximation for the related problem of PACKING INTERVALS IN INTERVALS, also introduced by Winkler and Zhang in [10].