The research achievements of optical buffer based on optical fiber delay line in recent 10 years are introduced. The basic buffer element, dual loop optical buffer (DLOB), is introduced. Based on DLOB, some new structures of buffer for different applications are proposed, such as the buffer with big dynamics of delay from 1 to 9999 T and the eight wavelengths buffer. All of these buffers are operated at the bit rate above 2.5 Gb/s. A polarization-rotation-based optical buffer is proposed. The principle, key technologies and experimental results are introduced for all above buffers. At last, the advantages and development future are discussed.