A new design principle of optical burst switching (OBS) networks of ring configuration cooperating with static wavelength-division multiplexed (WDM) optical add/drop multiplexers (OADMs) is described. The paper indicates that wavelength-bypassing provided by the OADMs improves burst transport in several ways. For example, the bypassing makes the size of OBS switch fabric and mean hop-counts small. The paper focuses on burst loss rate performance. An optimum design to minimize burst loss rate in an OBS ring network under a given WDM level and the number of nodes is formulated through theoretical analysis. Simulation results show good agreement with the theory.