We consider single-hop lightwave networks with nodes interconnected using wavelength division multiplexing where a time division multiplexing(TDM) switching is used. The nodes are equipped with tunable transmitters and receivers. The transmission duration is composed of two elements : the packet transmission time and the tuning time of the system``s transmitters and receivers. To find the efficient time-wavelength schedule, we introduce the concept of the genetic algorithm which is search techniques for global optimization in a search space. We see the time-wavelength scheduling problem as the bin-packing problem, one of the grouping problem, develop the algorithm based on the grouping genetic algorithm.