Study On Stimulated-scattering-induced Slow Light In A Single Mode Optical Fiber

The stimulated scattering especially the stimulated Brillouin scattering (SBS) has already become a hot topic in the research of slow light, as it has many advantages such as low power threshold, tunable wavelength, controllable group velocity, and what is important, the high compatibility with the existing optical communication systems. It has great potential usage in the district of controllable optical delay, buffering, data synchronization, etc. Although the bandwidth of SBS is only several tens of MHz, many ways of constructing broadband gain spectra have been proposed for propagation of higher bit rate signals so far, and the decline of the delay in the SBS process can be compensated by increasing the power of the pump beam. These broadband gain spectra can provide enough bandwidth for the practical signals, but in the long transmission of the slow-light process, large pulse distortion still can not be avoided.On the bases of the studies above, under the steady-state small-signal approximation we constructed the flat-top gain spectrum which can reduce the pulse distortion in the SBS-induced slow-light process essentially. At last we also discussed the large signal case (that is pump depletion or gain-saturation) of SBS, which provides theoretical guidance for the actual use of the slow light.The innovation of this paper includes:1. Using the method of counteraction of the gain and the loss, by setting the frequency interval oftwo broadband pumps (with different power) to two times of SBS frequency shift, the gain spectrum of the stronger pump is partially cancelled by the loss spectrum of the weaker one, a flat-top broadband gain spectrum is constructed. We theoretically proved that the distortion in the SBS-induced slow-light process can be essentially reduced using this gain spectrum.2. Furthermore, we got the special gain spectrum which brings no pulse broadening in theSBS-induced slow light process using the same method. We anticipate that the bit rate of the signal pulse for slow-light propagation in the fiber can be greatly improved using this method.3. We studied the large signal case of SBS-induced slow-light. The specific theoretical analysisof it was shown. We can see that under large signal situation the effect of SBS will be reduced.