Stimulated Brillouin scattering gain profile characterization by interaction between two narrow-linewidth optical sources

Abstract

We report on results from the characterization of Stimulated Brillouin Scattering (SBS) spectra for standard single-mode fiber produced by the interaction between two counter-propagating tunable laser sources (TLS) using one as the probe signal to measure and the other as the pump, sweeping a wide span around the signal. Assuming TLS linewidth negligible against SBS gain bandwidth, we measure SBS spectrum for a wide range of pump and probe signal power levels and study the evolution of relevant SBS parameters such as linewidth and gain profile. High signal to noise ratio measurements allows analyzing the evolution of the SBS gain profile from Lorentzian to Gaussian as predicted by current theory of SBS and the use of SBS response for filtering applications.

Stimulated Brillouin scattering in SM ZBLAN fiber

“…Since the frequency shift is inversely dependent on lambda, a~6 GHz frequency shift is expected at 1.55 μm in bulk for the same composition. Our measurements differ due to the different pump/saturations conditions used in our experiments [15]. Fig.…”

“…Therefore, we can stipulate that the actual shape is in-between a Gaussian and Lorentzian function, as shown on the high frequency side of the BGS. Since we are far from the high gain saturation regime as described by Villafranca and Lázaro [15], the presence of a Gaussian nature may indicate inhomogeneous broadening. From the observed maximum gain, we can calculate the Brillouin gain g B , from Eq.…”

“…As pointed out by Villafranca and Lázaro [15] the BGS depends strongly on the technique used for measurements. In fact, depending on the power difference between the pump and the seed, the bandwidth will act as a narrow Gaussian gain spectrum (high gain regime) or as a Lorentzian spectrum (low gain regime).…”

Impact of Optical Modulators in LTE RoF System with Nonlinear Compensator for Enhanced Power Budget

“…1(b), which was captured via an optical spectrum analyzer, BOSA 200 by Aragon Photonics. The undithered (S D (t) off) optical spectral at the output of DM and EM resulted in a linewidth of full width at half maximum (FWHM) of ~11.14 MHz, since SBS linewidth is typically around ~30 MHz [4], most propagating signals are back-reflected due to the formation of index grating. From Fig.…”

“…An index grating is formed when the propagating signal has a narrower linewidth than the SBS linewidth and subsequently energizes the back-reflecting Stokes wave [4]. An enhanced SBS threshold optical fibre was proposed as a solution in [5], but replacing the existing single mode fibre (SMF) infrastructure would not be cost effective [3].…”