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.
