The ytterbium-doped fiber amplifier offers a number of attractive features, including a broad-gain bandwidth and a high efficiency, due in large part to its freedom from various competing processes seen in other rare-earth dopants. Here we discuss the main features that influence design and possible applications of ytterbium-doped fiber amplifiers.

Ytterbium-doped fiber amplifiers

This paper reviews the developments of a distributed strain and temperature sensing technique that uses Brillouin scattering in single-mode optical fibers. This technique is based on strain- and temperature-induced changes in the Brillouin frequency shift. Several approaches for measuring the weak Brillouin line are compared. >

Development of a distributed sensing technique using Brillouin scattering

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 generation wave efficiency with respect to phase mismatch in the four-wave mixing process is clarified experimentally in a single-mode fiber transmission line at 825 nm wavelength. The generated power of approximately 20 pW is measured successfully for input signal powers below 1 mW by the technique utilizing a heterodyne receiver and lock-in detector. The calculated efficiency as a function of the equivalent frequency separation can well explain and reflect the results obtained experimentally. Furthermore, the efficiency at zero chromatic dispersion wavelengths of 1.3 and 1.55 μm is also discussed considering chromatic dispersion slope against wavelength.

Phase-mismatch dependence of efficiency of wave generation through four-wave mixing in a single-mode optical fiber

Exploiting photon–phonon coupling in nanoscale silicon waveguides could enable a host of powerful features in photonic devices. Using a hybrid photonic–phononic waveguide structure, Shin et al. show stimulated Brillouin scattering nonlinearities and gain, which offers new on-chip signal-processing abilities.

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Tailorable stimulated Brillouin scattering in nanoscale silicon waveguides

Stimulated Brillouin Scattering (SBS) has recently been observed in low-loss monomode fibers at power levels of only a few milliwatts. This article reviews the increasingly important influence which SBS will have on the design and operating range of future optical communications systems which employ low-loss fiber and narrowband laser transmitters. The important dependence of the SBS gain and threshold on the spectrum and modulation parameters of the optical transmitter is described. Possible techniques for suppressing SBS in optical communications systems are discussed.

D. Cotter

Papers

Stimulated Brillouin Scattering in Monomode Optical Fiber