An active optical fiber loop is consisted of a low noise EDFA, an optical band pass filter with 0.8 nm pass band, and 10 439 m standard SMF fiber. The detailed test was performed and good test results were obtained, which indicated that the active optical fiber loop has a good ability of signal pulses replicating. Based on the active optical fiber loop, an optical buffer unit was designed. The principle of the optical buffer was explained and the definition of unit storage time and maximum storage time were given. Experiment results indicate that the optical buffer unit can restore the input optical pulse signal. It has a minimum storage time nearly 50 μs, and the maximum optical pulse signal replicators are above 500. In another words, the maximum storage time is nearly 25 ms.