An Ethernet switch is used to dynamically reconfigure an optical network having a fixed optical layer. The Ethernet switch is incorporated into a transmission node of the optical network to selectively route data streams received through its input channels to one of the output channels. The data streams at the output channels are multiplexed into multiple wavelength channels of a multiplexed optical signal, and the wavelength channels are selectively dropped at local nodes of the optical network. In addition, the Ethernet switch can be used to reroute data from a single data stream to multiple wavelength channels, and thereby perform sub-wavelength multiplexing.