Suppression of stimulated brillouin scattering effect using self-phase and cross-phase modulation

Abstract

Stimulated Brillouin scattering (SBS) is a resonant nonlinear optical interaction with the material that results in transmitted light being scattered back towards the input. Although high power lasers are available to overcome the intrinsic loss of standard single mode optical transmission fibers (0.2 to 0.3 dB/km) but SBS places an upper limit on the optical power that can be transmitted through the link. This optical power limitation gets worse as the length of the fiber is increased. It is totally undesirable for many other applications because it limits the amount of optical power that can be used in a fiber. Recently, there is an increasing interest in reducing the SBS effect for applications such as optical links, fiber amplifiers and lasers, nonlinear devices, fiber to the home etc. where high optical power is required. Usually, SBS normally has a lower threshold power ( 1.4 mW) than other nonlinear effects. In this thesis work, we have studied a novel SBS suppression mechanism in optical transmission system utilizing the effects of self phaseand cross phase modulation which causes spectral broadening of the propagating signal and thereby suppress the SBS effect. We have established the analytical model for spectrum broadening factor using self phase modulation (SPM) and cross phase modulation (XPM) by solving the nonlinear Schrödinger equation. SBS threshold is dependent on optical sources spectral width and spectral broadening due to SPM and XPM ultimately enhances the threshold level. Our numerical simulation results show that this method will increase the SBS threshold power significantly through choosing the proper fiber length; such high level SBS threshold power can suppress the SBS sufficiently and even completely. The results are evaluated at different input power and varying transmission distance and it is found that XPM effect plays more active role than SPM for same amount of channel power. Our findings of this research will be useful to design a fiber-optic based wavelength division multiplexing system where transmission of higher power is an important factor.