Acoustic Waves In Optical Fibers Research Articles

Characterization of flexural acoustic waves in optical fibers using a fiber-tip interferometer

An experimental study using a fiber-tip interferometer (FTI) to characterize traveling flexural acoustic waves (TFAWs) along an optical fiber is reported. The measurements carried out with the FTI are performed following two different procedures: one of them relies on adjusting the interferometer at the quadrature condition and the other extracts the information from the amplitudes of the fundamental and second harmonic of the interference signal. From our measurements, the detection limit of the FTI is 0.5 nm and the upper limit of the linear regime is 30 nm. These results validate the use of the FTI to detect nanometric displacements associated to the amplitude of acoustic waves along an optical fiber. Parameters such as the acoustic wavelength, attenuation coefficient, and phase velocity are measured for a range of acoustic frequencies around the 2 MHz region. Furthermore, and supported by the in-fiber acousto-optic (AO) effect produced by TFAWs, parameters associated to an acoustic wave packet such as the group velocity and the group attenuation coefficient are also determined. This set of experimental results provide useful information of the mechanisms underlying the propagation of TFAWs along an optical fiber and its corresponding AO effect.

Numerical characterization of piezoelectric resonant transducer modes for acoustic wave excitation in optical fibers

The control of light in optical fibers by acoustic waves often requires a piezoelectric transducer as acoustic driver. As the fiber acoustic excitation depends on the deformation and frequency of the transducer, the analysis of the resonances and piezo mechanical behavior provides more efficient operation for acousto-optic devices. In this paper, an acousto-optic modulator is modeled using a three-dimensional finite element method in order to investigate the effect of the vibration modes of a piezoelectric disc in the excitation of acoustic waves in a fiber segment. The results indicate that in specific resonances, transducer radial and thickness modes are useful for the excitation of flexural and longitudinal acoustic waves in optical fiber.

Characterization of flexural acoustic waves in optical fibers using an extrinsic Fabry–Perot interferometer

A setup for the characterization of flexural acoustic modes in optical fibers is reported. An optical system based on an extrinsic Fabry–Perot interferometer is developed in order to measure the mechanical deformations of the fiber caused by a standing acoustic wave. Measurement of the excitation frequency and period allow estimation of the acoustic phase velocity propagating in a standard single mode and in a photonic crystal fiber.

Measurement of the frequency response induced by electrostriction in optical fibers

Accurate measurements of the frequency response of the nonlinear refractive index induced by the combined effects of Kerr nonlinearity with electrostrictional excitation of acoustic waves in optical fibers are presented. A detailed experimental investigation of both standard (zero-dispersion wavelength,lambda(0) approximately 1.31microm) and dispersion-shifted (lambda(0)=1.55microm) single-mode fibers showed the presence of several resonant peaks induced by the electrostrictive nonlinearity in the fiber structure. This investigation has provided better insight into the frequency behavior of the electrostriction-induced acoustic waves in optical fibers.

Measurement of the refractive-index modulation generated by electrostriction-induced acoustic waves in optical fibers

The refractive-index modulation generated in optical fibers by electrostriction-induced acoustic waves is investigated directly by a pump-probe measurement technique in a 1-km-long fiber Sagnac-loop interferometer. Pump pulses propagating unidirectionally around the loop generate transverse acoustic waves that produce a time-dependent relative phase shift for the probe pulses. The consequent interferometer transmission changes are used as a measure of the acoustic interaction. The acoustic impulse response function of the fiber is measured by use of short optical pulses with a 1-MHz repetition rate. The response consists of a series of peaks separated by ~21 ns with a maximum value of refractive-index modulation of -1.1 x 10(-11) generated by the 230-pJ pump pulses. At a higher pulse repetition rate of 100 MHz additional temporal structure is generated in the 0-5-ns period after the pump pulse, leading to a response similar to that observed in longrange soliton interaction.

Elastic waves in rods and optical fibers

This paper is a review of elastic waves in rods. This mature subject has important new consequences in optical fibers. The modulation or scattering of light by acoustic waves in optical fibers can be either harmful, as in catastrophic stimulated backward Brillouin scattering, or it can be put to practical use. While much of the paper is a tutorial description of basic knowledge about rod vibrations, several experiments are described that involve the interaction of light with vibrations in optical fibers. These include light modulation by thermally excited rod modes in an optical fiber, Brillouin gain measurements in fibers that are both acoustically and optically guiding, and some optical communication applications of stimulated Brillouin scattering. Reference is also made to other uses of acousto-optics in fibers.

Long-range interaction of picosecond solitons through excitation of acoustic waves in optical fibers

We present the theory of electrostrictional interaction of soliton pulses in optical fibers. Solitons excite acoustic waves propagating in the direction transverse to the fiber axis. Scattering of optical radiation on these waves leads to a timing jitter of the optical pulses arrival time. We consider this effect as nonlinear self-scattering of light on acoustic waves. Because of the fact that a value of acoustic lifetime can reach a value of about 100 ns self-scattering on acoustic waves can be observed for a single optical pulse as well as for an optical pulse sequence as a whole. The value of single soliton self-frequency shift due to excitation of acoustic waves as a function of soliton duration have been obtained. For soliton duration τsol > 14 ps an acoustic wave soliton self-frequency shift is larger than the Raman soliton self-frequency shift.

Elastic waves in rods and optical fibers

This talk reviews elastic waves in rods, with mention of their possible importance in optical fibers. The formal solution of the boundary value problem of the three-dimensional theory of elasticity for waves in rods was given over a century ago by Pochhammer and Chree. It was only about 50 years ago that important computations were done that enabled calculated results to be compared with experimental data for longitudinal waves [D. Bancroft, Phys. Rev. 59, 588–593 (1941)] and flexural waves [G. E. Hudson, Phys. Rev. 63, 46–51 (1943)]. The modulation or scattering of light by acoustic waves in optical fibers can be either harmful as in catastrophic stimulated backward Brillouin scattering [E. P. Ippen and R. H. Stolen, Appl. Phys. Lett. 21, 539–541 (1972)] or it can be put to practical use as has been attempted in devices such as acoustically mode-locked fiber lasers [Phillips et al., Opt. Lett. 14, 680–682 (1989)].