The advantages and the background of the Optical Burst Switching networks are reviewed based on a comparison study with wavelength-routed networks and Optical Packet Switching networks. Then the key attention-drawing issues concerning further develop of the OBS networks are analyzed. Currently, lots of effort has been taken in developing proprietary signaling protocols for resource reservation in OBS networks, the framework of OBS core switching node and edge routers. On the other hand, some related topics, such as contention resolutions strategy, QoS support strategy, control and scheduling algorithms, and hardware implementation issues about Tunable Wavelength Converter, Fiber Delay Line based optical buffers, high speed optical switches, are all need further research. All these issues will be reviewed in this work. At last, some problems not yet been studied in current works are presented, and further research directions are proposed.