| The study of controllable pulse delaying and advancement in an optical fiber is very necessary because it can be potentially used for the development of fast-access memories and optically-controlled delay lines which plays an important role in the realization of all-optical communication system. Now the main problems are to increase the pulse delay and reduce the pulse width.Usually, the broadening of a pulse is due to two factors: SBS gain broadening and dispersion broadening which includes GVD and TOD, and thus it is impossible to get a zero-broadening pulse for an original un-chirped pulse in a linear slow-light system. We show in theory that the two GVD parameters in the normal and anomalous dispersion regions can be modulated to counteract so that we can get a zero-GVD-broadening pulse by using two broadband pumps with different powers and spectral widths. Using the method of dispersion compensation, the third-order dispersion (TOD) effect can also be canceled out simultaneously.Besides, the pulse compression occurs in the anomalous dispersion region also. The gain broadening in the first slow-light stage can also be compressed in the second stage. Thus we can get a nearly zero-broadening pulse, which remains the time delay. We calculate the root-mean-square (RMS) width of the pulse in our paper to avoid some ignorance of the sub-pulses.We also studied SBS fast light and its experimental setup. We know, owing to the effect of gain saturation, the fast light experience strong loss and cannot have long distance propagation. Here we make SBS fast light propagate in the fiber ring cavity in order to get an advanced pulse.Through the theory we shown and the experimental setup of SBS slow light and fast light, it is possible to get a delay pulse with low distortion. We believe the method will be useful for further study. Our process is linear and it can be replaced by almost all the achieved method for slow-light system and different pump beam spectrum. |
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