In this paper, we propose a new composed buffer structure termed as wavelength converted broadcast-selective (WCBS). It copies each packet after conversion to all fiber delay lines, and makes the packet management flexible and efficient. By rearranging the packet waiting queue, the highest priority packet can leave the buffer without considering the existing queue, which makes preemption possible. Moreover, we construct an OPS node architecture employing the as-proposed WCBS buffer in output-buffered pattern. Some proper switching strategies are introduced to operate the switching node effectively. An analysis model is established to describe the packets in the node. The minimum packet loss performances under different traffic loads with different buffer parameters are calculated. The results are further verified by simulations. It implies that the WCBS buffer improves the performance of high priority packets effectively, especially when the high priority packet load is low.