As the demand for speed and bandwidth in communications networks increases, new approaches to switching and routing are under study. Now researchers at the University of Illinois at Urbana-Champaign have developed an all-optical device that rapidly and accurately shifts the frequency of optical data in return-to-zero format between channels.At the heart of the shifter, which they described at the March meeting of the American Physical Society in Austin, Texas, is a standard optical phase modulator that has an optical waveguide diffused in a lithium niobate substrate. Applying a microwave signal to a gold electrode deposited on the substrate controls the properties of the waveguide, enabling the user to dynamically shift the frequency of optical pulses within it.