Contents I. Introduction
Optical networks using wavelength-division multiplexing (WDM) provide large capacity, but providing access to that capacity in a way that is simple enough to be economical is challenging. In particular, the large quantity of aggregate capacity available in such networks is often inaccessible owing to constraints imposed by interactions among optical fibers, wavelengths on these fibers, electronic routers, and add-drop multiplexers (ADMs). This problem impacts both the design of optical networks (to make good use of their raw bandwidth) and the algorithms for fitting offered traffic into the network. For example, a particular placement of traffic on wavelengths that respects the (electrical) bandwidth at each given node may nevertheless be infeasible if the traffic destined for a node is spread out over more wavelengths than the node has wavelength ADMs.
In this paper, we consider an ADM to comprise single wavelength-tunable receiver/transmitter (transceiver) pair along with the attending equipment, such as filters, to access the fiber. As we discuss in Section III-A, the transmitter or receiver may under certain conditions be constrained to a single wavelength without any loss in performance.
