The problem of configuring fiber delay lines (FDLs) for recirculation FDL buffer in a slotted and synchronous optical packet switched network is researched in this paper. By studying the distributions of the lost packet in switch with uniform degenerate buffers configuration, it is found that the lost packets arouse by the taking up of small granularity FDL are much more than the lost packets arouse by the taking up of large granularity FDL. So a good scheme to cut down the Packet Lost Ratio is by increasing the proportion of the small granularity FDL at a cost of decreasing the proportion of the large granularity FDL. Simulation results show this scheme is effective