We present three dynamic routing and wavelength assignment (RWA) algorithms that are intended for multifiber WDM networks without wavelength converters. For networks with a large number of wavelengths per fiber and/or a large number of fibers per link, our algorithms exhibit particularly good performance, and one of them significantly outperforms other existing algorithms. In response to a connection request, our algorithms first select a physical route among a set of predetermined routes on the basis of some per-route variables. The algorithms then select a wavelength to be used with the selected route. This paper illustrates how we can rethink the criteria for route selection in multifiber networks. We also suggest a method of selecting the set of predetermined routes to balance the traffic load. Our simulation results illustrate that this method exhibits significantly lower blocking probability than the traditional shortest-route-based method. Thus, this paper also illustrates that the choice of predetermined routes can significantly affect the blocking probability of an RWA.