All-Optical Label Switching (AOLS) is a new technology that performs forwarding without any Optical-Electrical-Optical (OEO) conversions. In this report, we study the problem of routing a set of requests in AOLS networks with the aim of minimizing the number of labels required to ensure the forwarding. In order to spare the label space, we consider label stacking, allowing the configuration of tunnels. We study particularly this network design problem when the network is a line. We provide an exact algorithm for the case in which all the requests have a common source and present some approximation algorithms and heuristics when an arbitrary number of sources are distributed over the line. We contrast the performance of our proposed algorithms by simulations., OPTx-editorial-board=yes, OPTx-proceedings=yes, OPTx-international-audience=yes