One of the difficulties of optical packet switched networks is buffering optical packets in the network. Currently, one solution that can be used for buffering in the optical domain is using long fiber lines called Fiber Delay Lines (FDL). However, FDLs provide only a small and fixed amount of delay. Thus, burstiness of Internet traffic and over-utilizations cause high packet drop rates in small and fixed delayed OPS networks. Recently, we proposed a new network architecture using a XCP-based congestion control algorithm for OPS WDM networks with pacing at edge nodes for minimizing the buffer requirements at core nodes. In this paper, we investigate input and output optical switch architectures for minimizing the size of optical switching fabric with the proposed network architecture. We show the number of FDLs and switch size requirements of architectures depending on FDL granularity and packet size distribution.