We present a detailed overview of stimulated Brillouin scattering (SBS) in
 single-mode optical fibers. The review is divided into two parts. In the first part,
 we discuss the fundamentals of SBS. A particular emphasis is given to analytical
 calculation of the backreflected power and SBS threshold (SBST) in optical fibers
 with various index profiles. For this, we consider acousto-optic interaction in the
 guiding geometry and derive the modal overlap integral, which describes the
 dependence of the Brillouin gain on the refractive index profile of the optical
 fiber. We analyze Stokes backreflected power initiated by thermal phonons, compare
 values of the SBST calculated from different approximations, and discuss the SBST
 dependence on the fiber length. We also review an analytical approach to calculate
 the gain of Brillouin fiber amplifiers (BFAs) in the regime of pump depletion. In the
 high-gain regime, fiber loss is a nonnegligible effect and needs to be accounted for
 along with the pump depletion. We provide an accurate analytic expression for the BFA
 gain and show results of experimental validation. Finally, we review methods to
 suppress SBS including index-controlled acoustic guiding or segmented fiber links.
 The second part of the review deals with recent advances in fiber-optic applications
 where SBS is a relevant effect. In particular, we discuss the impact of SBS on the
 radio-over-fiber technology, enhancement of the SBS efficiency in Raman-pumped
 fibers, slow light due to SBS and SBS-based optical delay lines, Brillouin
 fiber-optic sensors, and SBS mitigation in high-power fiber lasers, as well as SBS in
 multimode and microstructured fibers. A detailed derivation of evolutional equations
 in the guided wave geometry as well as key physical relations are given in
 appendices.

Stimulated Brillouin scattering in optical fibers

The scattering of laser light by acoustic phonons confined within a photonic crystal fibre reveals unexpected highly nonlinear acoustic modes that behave like the Raman-active modes of a molecule.

/pdf/tightly-trapped-acoustic-phonons-in-photonic-crystal-fibres-doebrecdhj.pdf

Tightly trapped acoustic phonons in photonic crystal fibres as highly nonlinear artificial Raman oscillators

We provide a complete experimental characterization of stimulated Brillouin scattering in a 160 m long solid-core photonic crystal fiber, including threshold and spectrum measurements as well as position-resolved mapping of the Brillouin frequency shift. In particular, a three-fold increase of the Brillouin threshold power is observed, in excellent agreement with the spectrally-broadened Brillouin gain spectrum. Distributed measurements additionally reveal that the rise of the Brillouin threshold results from the broadband nature of the gain spectrum all along the fiber and is strongly influenced by strain. Our experiments confirm that these unique fibers can be exploited for the passive control or the suppression of Brillouin scattering.

https://hal.archives-ouvertes.fr/hal-00269048/document

Complete experimental characterization of stimulated Brillouin scattering in photonic crystal fiber

There is provided a system, apparatus and methods for the laser drilling of a borehole in the earth. There is further provided with in the systems a means for delivering high power laser energy down a deep borehole, while maintaining the high power to advance such boreholes deep into the earth and at highly efficient advancement rates, a laser bottom hole assembly, and fluid directing techniques and assemblies for removing the displaced material from the borehole.

Method and system for advancement of a borehole using a high power laser

The removal of material from the path of a high power laser beam during down hole laser operations including drilling of a borehole and removal of displaced laser effected borehole material from the borehole during laser operations. In particular, paths, dynamics and parameters of fluid flows for use in conjunction with a laser bottom hole assembly.

Methods and apparatus for removal and control of material in laser drilling of a borehole

We present extensive stimulated Brillouin scattering (SBS) results from experiments and modeling for four different photonic crystal fibers (PCFs) with core diameters ranging from 8 to 1.7 μm. These results reveal several SBS characteristic features of small-core PCFs, high thresholds, and acoustic peaks, which are due to their antiguiding nature and highly multimode acoustic character. The nature of what we believe to be new acoustic modes is examined in the light of the large variations observed in the Brillouin gain, Brillouin threshold, and Brillouin shift with decreasing core diameter and optical wavelength.

Unique characteristic features of stimulated Brillouin scattering in small-core photonic crystal fibers

Stimulated Brillouin scattering (SBS) generated from noise in small-core photonic crystal fibers (PCFs) exhibits a strong dependence on pump polarization. The polarization dependence of two small-core PCFs is investigated, yielding unexpected results. Both fibers exhibit birefringence resulting in a 90° polarization dependence for the SBS and a 3 dB difference in the SBS threshold between polarizations corresponding to minimum and maximum SBS, respectively. Surprisingly, the transmission of the smaller-core fiber also exhibits a 180° polarization dependence at lower powers due to polarization-dependent loss.

Polarization dependence of stimulated Brillouin scattering in small-core photonic crystal fibers

We study through experiment, calculation and simulation the frequency dependence of depolarized GAWBS observed in four different photonic crystal fibers and extend the results to others through simulation. In two of the fibers studied, high frequency modes (>; 1 GHz) are observed in addition to the usual lower frequency torsional radial (TR) modes. The acoustic modes responsible for GAWBS are characterized through a combination of simulations and experiments. The calculations are done using the silica rod approximation, which is valid for PCFs with a low to intermediate air-fill fraction or with a very high air-filling fraction. Further simulations extend the range of photonic crystal fibers in which acoustic modes can be characterized. These are used to study the dependence of the acoustic mode frequency on key fiber parameters such as the ratio of air to silica across the whole cross section (κ) and the lattice pitch (Λ) .

Dependence of Frequency Shift of Depolarized Guided Acoustic Wave Brillouin Scattering in Photonic Crystal Fibers

Guided acoustic wave Brillouin scattering (GAWBS) in PCFs is altered by the air-silica structure of the inner cladding and does not depend on the cladding diameter as with standard fibers. This dependence is investigated.

Depolarized guided acoustic wave Brillouin scattering in photonic crystal fibers

We study through experiment, calculation and simu- lation the frequency dependence of depolarized GAWBS observed in four different photonic crystal fibers and extend the results to others through simulation. In two of the fibers studied, high fre- quency modes ( GHz) are observed in addition to the usual lower frequency torsional radial (TR) modes. The acoustic modes responsible for GAWBS are characterized through a combination of simulations and experiments. The calculations are done using the silica rod approximation, which is valid for PCFs with a low to intermediate air-fill fraction or with a very high air-filling fraction. Further simulations extend the range of photonic crystal fibers in whichacousticmodescanbecharacterized.Theseareusedtostudy thedependenceoftheacousticmodefrequencyonkeyfiberparam- eters such as the ratio of air to silica across the whole cross section and the lattice pitch .

http://ieeexplore.ieee.org/iel5/50/5680666/05634049.pdf

John E. McElhenny

Papers

Unique characteristic features of stimulated Brillouin scattering in small-core photonic crystal fibers

Polarization dependence of stimulated Brillouin scattering in small-core photonic crystal fibers

Dependence of Frequency Shift of Depolarized Guided Acoustic Wave Brillouin Scattering in Photonic Crystal Fibers

Depolarized guided acoustic wave Brillouin scattering in photonic crystal fibers

Dependence of Frequency Shift of Depolarized Guided Acoustic Wave Brillouin Scattering in