Study On Applications Of Stimulated Brillouin Scatterng In Optical Fibers

Stimulated Brillouin scattering (SBS) can be described classically as anonlinear interaction between the pump and Stokes fields through the acoustic wave,where the acoustic wave is generated by the pump field through the electrostriction. Theperiodic modulation of refractive index of the medium is induced by the acoustic wave,which scatters the pump wave by Bragg diffraction. Due to the Dopper shift of thegrating moving at speed of sound, the frequency of Stokes wave is down-shifted. Thescattering process can be regarded as a pump photon is destructed, while a Stokesphoton and an acoustic phonon are produced in quantum mechanics. The threshold ofSBS in fiber is lower than those needed for other medium because of the restriction ofoptical waveguide structure. The SBS in optical fiber has been widely used in the fieldsof slow light, fiber laser, fiber-optic sensors, microwave photonics, etc. This papermainly studies the applications of SBS in optical fiber to slow light and fiber lasers.For the application of SBS to slow-light, the influences of pulse input pump power,input signal pulse-width, and chirp on the delay time, output pulse-width, and distortionare investigated. The results show that, the relative delay time of signal light isenhanced with the increased pump power, while accompanied by the additional pulsebroadening; The introduction of initial chirp for input signal pulse is helpful forsuppressing the pulse broadening, but the relative delay time of signal light is worsened.Hence, there exists an optimization ranges both for pump input power and initial chirp.For the application of SBS to fiber lasers, the influences of system parameters on itsinput-output characteristics are investigated both for linear and ring cavities. Resultsshow that, the lasing thresholds increases with the increased pumping order clearly; Thelonger fiber and larger coupling coefficient are helpful for reducing the lasing threshold.On the other hand, the threshold improvement saturates for excessively injected pumppower and coupling coefficient; There exists an optimization ranges both for fiberlength and coupling coefficient.