A WDM-based PCN architecture is proposed. Based on the broadcast nature of WDM star couplers, this WDM-based architecture gains several advantages over the current prominent ATM-based PCN architecture: (1) a fast hand-off scheme for roaming terminals, (2) an easy multicast routing implementation for mobile environment, and (3) a less number of continuous reconnections. Based on the proposed architecture, a wavelength offset conflict problem might occur when mobile terminals move into neighboring cells. A wavelength assignment scheme is proposed to assign the wavelength and offset on the star coupler for each connection so that the offset conflict rate is kept as small as possible. Simulation results show that the proposed wavelength offset assignment scheme performs much better than the random assignment scheme in terms of offset conflict rate.