Tunable wavelength conversion of a 10-Gb/s, return-to-zero ON-OFF-keyed (RZ-OOK) signal has been carried out in a silicon (Si) nanowire waveguide (Si nanowire) using a pump-probe configuration and cross-phase modulation (XPM), followed by a tunable filter. This filter spectrally emulated the pass-band of a commercial 50-GHz DWDM arrayed waveguide grating (AWG). The tunability of the wavelength conversion process was demonstrated over a range of 20 nm, limited only by the amplifiers and the filter, while keeping the 10-9-BER receiver sensitivity penalty of the converted signal to a 0.5-dB maximum. A comprehensive model of wavelength conversion by XPM (XPM-WC) was developed, which took into account two-photon absorption, the Kerr effect, and free-carrier generation. The results of the model demonstrate good agreement with the experiment, especially with respect to the observed spectral broadening. The numerical model was also used to assess the dominant contribution among the various mechanisms within the context of XPM-WC, and to investigate the potential of multicasting by XPM in the nanowire. © 2006 IEEE.