The answer to this conundrum is to reduce the overall complexity of the network by lowering the number of network elements, replacing copper networks with optical, and improving the reliability of the network as a whole. These can be done, but in some cases, they run contrary to the direction that the network has taken. For example, until recently, optical components were corralled in the physical layer as SONET or SDH devices, providing physical transport capability for ATM and frame relay networks, which in turn provided switching fabric for Layer 3 protocols, such as IP. With the arrival of wavelength division multiplexing (WDM) in the late 1990s, an additional optical sublayer was created below SONET/SDH, and at the end of the 1990s, we saw the arrival of optical switching, which burrowed into the space between the physical layer (SONET/SDH) and the switching layer (ATM/frame relay). This resulted in a growth in complexity as the three-layer protocol stack became a five-layer protocol.

Today, a move is afoot to collapse the stack again by evolving to an all-optical network. Current product offerings make it possible to deploy optical networks not only in the long haul, but in the metro and access regions as well.