Research On Slow Light Based On Stimulated Brillouin Scattering In Optical Fibers

Slow-light based on fiber has been a topic since 2004, and especially its prospect applications on all-optical communication devices, such as information synchronizer, buffer, switch and time multiplexer, have attracted many researchers’attention. We research stimulated Brillouin scattering (SBS) slow-light both from theory and experiment.Firstly, research background and progress of slow light are investigated. And slow light via stimulated Brillouin scattering is the most practical method because of its numerous advantages.Theoretically,from K-K relations we see Brillouin amplification will cause medium phase refractive index to increase large (normal dispersion occur) and group velocity reduces.Physical process for spontaneous and stimulated Brillouin scattering are introduced here.It’s important characteristic parameters,including threshold, gain spectrum and Brillouin frequency shift are measured using optical heterodyne detection method.Then, based on three-wave coupled equation, taking fiber losses into consideration,we deduce Stokes wave complex wavenumber, phase index, gain and group index, numerically simulated them via MATLAB.We can easily conclude the three reach their maximum value simultaneously nearby the gain center, which analyzes slow light physical mechanism basically.Finally, theory support for Brillouin gain spectrum broadening and principle of phase modulation pump to be multiline are explained.Each pump spectra produces dependent Brillouin gain area, and they compose a broad gain spectrum. Also total gain and total phase index are numerically simulated them via MATLAB.According to the theoretical analysis above, narrow-band SBS and broad-band SBS system are designed. In the narrow-band SBS system, we match frequency condition between pump and input signal manually due to its narrow gain spectrum. We get a delay of 8ns for a pulse with the 200ns bandwidth.In the broad-band SBS system, we modulate pump light using a phase-modulator to broad gain spectrum to 450MHz, and finally we obtain a delay of 32ns for a pulse with the 500ns bandwidth when gain is 15dB.In the end, we present sevearl prospects for slow-light research to lay a foundation for further study of Slow light topic.