STIMULATED BRILLOUIN SCATTERING (SBS) CHARACTERIZATION IN MODERN FIBRES AND A TECHNIQUE OF SLOW LIGHT GENERATION

Abstract

Stimulated Brillouin scattering (SBS) is one of the recent technology that is being developed to generate slow light in optical fibres. It is one of the simplest and most applicable methods of slow light production. Slow light is the reduction of group velocity for optical pulses propagating through a dispersive material. SBS in silica based optical fibres is a fundamental nonlinear phenomenon considered as interaction of light and pressure wave in a material. The same scattering process can be viewed quantum mechanically as if annihilation of a pump photon creates a Stokes photon and an acoustic phonon simultaneously. SBS process in optical fibres occurs at a frequency shift of approximately 11GHz. In this work a high power laser pump was used to obtain the Brillouin gain of a low power signal of -10 dBm. Four single mode modern fibres namely, standard fibre (STD), large area fibre (LA), reach fibre (R) and reduced slope fibre (RS)of different optical characteristics were used in the study. Brillouin threshold for STD, LA, R and RS was compared and the effect of length on Brillouin threshold was determined. Variation of signal delay with pump power, fibre length and temperature in SBS slow light was studied. The effect of pump linewidth on Stokes power was also investigated. It was found that both the R and RS fibres had the highest Brillouin activity. Brillouin threshold of each of the four fibres decreased with increase in length of fibre. However, Stokes power was observed to increase with fibre length. Signal delay was realized for pump power between 27 dBm and 30dBm for STD, LA and RS fibre. A maximum delay of 7.6 ps was observed for STD fibre. However, signal speed up of 4.2 ps was realized for R fibre. It was also noted that signal delay increased with increase in fibre length. An increase in temperature resulted to a corresponding increase in Stokes power and signal delay of 1.6ps for RS. Moreover, increase in pump linewidth caused a decrease in Stokes power. This study is of great significance since it immensely contributes to practical applications in optical telecommunication, operation of SBS based optical sensors and information systems such as optical buffers, optical synchronizers and optical equalizers.