The demand for more bandwidth has lead to proposals for an all-optical network core. Due to inherent constraints of optical technology, only routers with small packet buffers are feasible to be implemented. In order to ensure efficient operation of such small-buffer networks, it is necessary to ensure that traffic is less bursty than in conventional networks. We propose a novel packet pacing mechanism that can smooth traffic bursts. Our theoretical analysis shows that our pacing scheme can guarantee that queue length of routers is BIBO stable. Experimental results from our prototype implementation show the effectiveness of our pacer on in terms of reduced network congestion and improving network throughput.