Pulse Compression And Doublet Broadband Pump Fast Light Via Stimulated Brillouin Scattering In Optical Fibers

Ultra-short optical pulses and controlling of the speed of a light signal have respective promising applications in high-capacity communications,molecular spectroscopy,all-optical routers,optical switching and microwave photonic filters.Optical pulse compression technology based on stimulated Brillouin scattering(SBS),offering advantages of high conversion efficiency,room temperature operation and so on,has attracted much interest recently.At the same time,SBS is viewed as one of the most effective ways to achieve fast light because of its benefits such as wavelength tenability.However,the effects of pump light and the relative frequency separation factor of two pump on pulse compression and fast light have not been well investigated.In this thesis,we firstly use the SBS analytical model and choose Runge-Kutta method to solve the three coupled amplitude equations.The effects of the shapes of pump pulse,including rectangle wave,the second order Gaussian wave,hyperbolic secant wave,Lorentz wave and triangular wave,the power and the pulse width of pump laser on the compression factor of signal pulse were discussed.The results indicate that the larger compression factor of optical signal pulse can be obtained with larger power,steeper raising edge and narrower pulse width of pump pulse.Finally,when pump power is 0.8125 W,the signal pulse with full width at half maximum(FWHM)of 400 ns is compressed to 200 ns approximately.Meanwhile,under the influence of Brillouin absorption spectrum,the effects of the pump pulse on compression factor and relative time advancement were researched.The simulation results show that when the FWHM of pump pulse gets narrower,the compression factor of signal pulse gets larger and the relative time advancement becomes smaller.The larger compression factor and relative time advancement can also be achieved with fiber with shorter length and absorptopn spectrum with narrower width.In addition,when the power spectrum of pump laser is doublet broadband Gaussian.,the transfer function in small signal regime is derived.Then the time advancement and the broadening factor of the output optical signal pulse can be acquired by numerically solving the transfer function,utilizing fast Fourier transform(FFT)algorithm.The results show that when the relative frequency separation factor of the two pump is set to be from 0.04 to 1.16,the time advancement of the optical signal pulse decreases gradually,while its broadening factor decreases first and then increases.The larger time advancement and the smaller broadening factor of optical signal pulse can also be obtained by using pump with larger power and the optical fiber with longer length.Consequently,the time advancement and the pulse distortion of the optical signal pulse can be optimized by adjusting the parameters such as the relative frequency separation factor,the pump power and the length of the optical fiber.Finally,a 224 ps Gaussian signal pulse can be advanced by 80 ps with small pulse distortion and broadening factor of 0.86.