Showing papers on "Brillouin scattering published in 1994"
TL;DR: In this paper, the polarization properties of stimulated brillouin scattering (SBS) in low birefringent optical fibers were evaluated using Stokes calculus, and it was found that the Brillouin gain for orthogonally polarized pump and probe wave is half (in dB) of the gain for identical polarization, and not equal as often mentioned in literature.
Abstract: The polarization properties of stimulated brillouin scattering (SBS) in low birefringent optical fibers were evaluated using Stokes calculus. It was found that the Brillouin gain for orthogonally polarized pump and probe wave is half (in dB) of the gain for identical polarization, and not equal as often mentioned in literature. Therefore the polarization factor is K=1/sub 1/2/ for complete polarization scrambling, and not K=2. The spontaneous SBS has the same state of polarization as the pump, and its degree of polarization is 33.3% for low pump powers and near 100% for high pump powers. The experimental results agree very well with the calculations. >
283 citations
TL;DR: Using Brillouin scattering the three independent elastic stiffness constants cij of singlecrystal cubic boron nitride have been measured: c11=820, c12=190, and c44=480 GPa as mentioned in this paper.
Abstract: Using Brillouin scattering the three independent elastic stiffness constants cij of single‐crystal cubic boron nitride have been measured: c11=820, c12=190, and c44=480 GPa. The resulting bulk modulus, 400 GPa, is in reasonable agreement with two independent determinations obtained from x‐ray measurements in a diamond anvil cell. Using the bulk modulus it is found that the x‐ray results are best fitted with a value of dB/dP=3.0.
268 citations
TL;DR: A novel distributed sensor that utilizes the temperature and strain dependence of the frequency at which the Brillouin loss is maximized in the interaction between a cw laser and a pulsed laser is presented.
Abstract: We present a novel distributed sensor that utilizes the temperature and strain dependence of the frequency at which the Brillouin loss is maximized in the interaction between a cw laser and a pulsed laser. With a 22-km sensing length, a strain resolution of 20 µ? and a temperature resolution of 2°C have been achieved with a spatial resolution of 5 m.
152 citations
TL;DR: In this article, a coherent self-heterodyne detection system employing a recently proposed frequency translator, a DFB laser diode, and erbium-doped fiber amplifiers is demonstrated.
Abstract: Time domain reflectometry of spontaneously Brillouin scattered lightwaves in a single-mode optical fiber is demonstrated with a coherent self-heterodyne detection system employing a recently proposed frequency translator, a DFB laser diode, and erbium-doped fiber amplifiers. Since the probe pulse frequency is up-converted by the translator by an amount approximately equal to the Brillouin frequency shift, the self-heterodyne beat frequency can be reduced to a sufficiently low frequency in the IF band. The system enables one-end measurement of the Brillouin frequency shift distribution in optical fibers with a single way dynamic range (SWDR) of 16 dB and a frequency resolution of 5 MHz for a spatial resolution of 100 m. >
131 citations
Patent•
29 Apr 1994
TL;DR: In this paper, a pumplaser is used to backscattered by spontaneous Brillouin scattering, which is then superimposed to a light wave derived from the pumpler and heterodyned at the detector.
Abstract: For the noninvasive investigation of optical fiber lines by means of heterodyne Brillouin spectroscopy light from a pumplaser (10) is directed into one end of the optical fiber line under investigation (16), so that spontaneous Brillouin backscattering is induced in the fiber (16). The light, which is backscattered by spontaneous Brillouin scattering, is superimposed to a lightwave, which is derived from the pumplaser (10), and heterodyned at the detector (46). The output signal from the detector is fed into a spectrum analyzer (50). A part of the light from the pumplaser (10) is directed into a ring resonator (38). The lightwave, which is derived from the pumplaser (10) and which is superimposed with the light, which is backscattered from the optical fiber line under investigation (16), is generated by stimulated Brillouin scattering inside the ring resonator (38).
106 citations
TL;DR: In this article, an efficient two-cell stimulated Brillouin scattering (SBS) pulse-compressor design that can be scaled to large laser-pulse energies is described and a numerical model has been developed that accurately predicts the performance of this system over a wide range of operating parameters.
Abstract: An efficient two-cell stimulated Brillouin scattering (SBS) pulse-compressor design that can be scaled to large laser-pulse energies is described and a numerical model has been developed that accurately predicts the performance of this pulse-compressor system over a wide range of operating parameters. The compression of a 2.5 J input pulse from a width of 15.8 to 1.7 ns is experimentally demonstrated with 80 percent energy efficiency. A design of an SBS pulse compressor to compress a 25 J pulse to a pulse width less than 1 ns with 80 percent energy efficiency is presented. >
71 citations
Patent•
29 Dec 1994
TL;DR: In this article, the effect of residual amplitude modulation has been mitigated by injecting the dithered optical signal into an optical device, such as a highly saturated amplifier, whose small-signal intensity response at the dither frequency dampens the residual amplitude amplitude modulation thereby decreasing the eye closure (alternatively, increasing the eye pattern opening).
Abstract: Stimulated Brillouin scattering has been effectively suppressed and the effect of residual amplitude modulation has been mitigated in a dithered optical transmitter by injecting the dithered optical signal into an optical device, such as a highly saturated amplifier, whose small-signal intensity response at the dither frequency dampens the residual amplitude modulation thereby decreasing the eye closure (alternatively, increasing the eye pattern opening). The optical device (e.g., the highly saturated amplifier) exhibits a low frequency cutoff (-3 dB) at a frequency greater than or equal to the inverse of the round trip time for a fiber span with the effective optical transmission length into which the optical signal power is launched. The dither rate is generally in the neighborhood of or below the low cutoff frequency.
70 citations
TL;DR: 5.1 dB of squeezing from a fiber interferometer pumped with a 1-GHz pulse source that successfully eliminates guided-acoustic-wave Brillouin scattering in significant frequency regimes is reported.
Abstract: We report 5.1 dB of squeezing from a fiber interferometer pumped with a 1-GHz pulse source that successfully eliminates guided-acoustic-wave Brillouin scattering in significant frequency regimes. The pulse source is a diode-pumped Nd:YLF laser actively mode locked at 1.314 microm. The squeezing results are consistent with the limits imposed by the Gaussian pulse shape and the detection quantum efficiency.
68 citations
AT&T1
TL;DR: In this article, the effects of phase-to-intensity noise conversion by multipath interference through Rayleigh scattering are counteracted simultaneously without introducing additional intermodulation distortion, both by single tone phase modulation and by dithering of the laser's optical frequency.
Abstract: Externally modulated AM-SCM lightwave systems employing optical power amplifiers, small linewidth DFB lasers and long optical feeder lines, face low stimulated Brillouin scattering threshold powers and phase-to-intensity noise conversion by multipath interference through Rayleigh scattering. We show that these problems can be effectively counteracted simultaneously without introducing additional intermodulation distortion, both by single tone phase modulation and by dithering of the laser's optical frequency. >
65 citations
TL;DR: In this article, the authors used stimulated Brillouin scattering to increase the modulation depth of a weakly-modulated optical signal by rejecting the forward travelling carrier power, achieving an improvement of 8 dB in link loss from 0.1 to 20 GHz.
Abstract: Stimulated Brillouin scattering is used to increase the modulation depth of a weakly-modulated optical signal by rejecting the forward travelling carrier power. For an input power of eight times the stimulated Brillouin threshold, an improvement of 8 dB in link loss from 0.1 to 20 GHz is achieved.
60 citations
Patent•
21 Jul 1994
TL;DR: In this paper, the backscattered optical radiation used to produce output signals is restricted to that resulting from Rayleigh scattering of light launched into a fiber 2 at a first wavelength and that in an anti-Stokes spectral band resulting from Raman or Brillouin scattering of optical radiation at the first wavelength.
Abstract: Optical time domain reflectometry methods and apparatus are proposed in which the back-scattered optical radiation used to produce output signals is restricted to that resulting from Rayleigh scattering of light launched into a fiber 2 at a first wavelength and that in an anti-Stokes spectral band resulting from Raman or Brillouin scattering of optical radiation at the first wavelength. A first set of output signals produced in dependence upon the anti-Stokes back-scatter may be normalized to the geometric mean of a second set of output signals, produced in dependence upon the Rayleigh back-scatter at the first wavelength, and a third set of output signals, produced in dependence upon Rayleigh back-scatter resulting from light launched into the fiber at the anti-Stokes wavelength. Growth in the intensity of optical radiation in a first Stokes (Raman or Brillouin) spectral band may be inhibited, so as to suppress stimulated scattering, for example by making the fiber 2 high loss at the Stokes wavelength and/or launching into the fiber 2, simultaneously with the pulse at the first wavelength, an additional pulse at a third wavelength equal to that of a Stokes spectral line resulting from inelastic scattering of optical radiation at the first Stokes wavelength. The first wavelength may be chosen so as to minimize the transmission loss, in view of the average losses at the first and detected wavelengths or the increase with wavelength of the launch power which can be used before stimulated scattering has a specified effect.
Patent•
20 Oct 1994TL;DR: In this article, the phase modulation of the optical beam was proposed to suppress Brillouin scattering in a lightwave AM-VSB CATV transmission system with an external modulator.
Abstract: Optical nonlinear effects, such as stimulated (Brillouin) scattering, cause disproportionate attenuation of transmitted optical signals and usually occurs only when the optical power exceeds a certain level. One of the most important types of nonlinear scattering which occurs in an optical fiber as the power of the optical signal is increased above a certain level is stimulated Brillouin scattering. Brillouin scattering limits the power density of an optical signal that can be injected into an optical fiber. This invention suppresses Brillouin scattering and, by so doing, permits the power density of the optical signal which is injected into an optical fiber to be increased approximately threefold before the Brillouin scattering threshold is reached. More specifically, in a lightwave AM-VSB CATV transmission system having an external modulator, the optical beam which is amplitude modulated with the CATV signals is also phase modulated with a sinusoidal signal having a frequency which is not less than twice the frequency of the highest CATV signal. The phase modulation of the optical beam suppress Brillouin scattering. With this invention the power density of the CATV signal can be increased approximately three fold before the threshold of Brillouin scattering is reached.
TL;DR: In this paper, a design theory of the four-wave mixing (FWM) devices using optical fibers is presented, and it is shown that the signal-to-idler conversion process in the zero-dispersion wavelength region yields the widest conversion bandwidth, and the conversion efficiency can be maximized by choosing the optimum fiber length.
Abstract: A design theory of the four-wave mixing (FWM) devices using optical fibers is presented. We find that the signal-to-idler conversion process in the zero-dispersion wavelength region yields the widest conversion bandwidth, and the conversion efficiency can be maximized by choosing the optimum fiber length. The maximum conversion efficiency thus obtained is proportional to the square of the input pump power, but is limited by the stimulated Brillouin scattering (SBS) process in the fiber. We show experimentally the improvement of the conversion efficiency by the SBS suppression and the validation of the proposed theory. >
TL;DR: In this paper, a model for the Raman effect as responsible for the self-frequency shift of solitons was constructed and compared with the measured Raman gain in silica fibers.
Abstract: A model is constructed for the Raman effect as responsible for the self-frequency shift of solitons. The effect is related to and compared with the measured Raman gain in silica fibers. The model is quantized and includes the thermal and the quantum noise of the optical phonons generating the Raman effect. It is shown that the Raman effect causes excess noise for ultrashort pulses and limits the squeezing of subpicosecond solitons.
TL;DR: In this article, the generation of phase-conjugate wave in a third-order nonlinear medium is discussed and the application of optical phase conjugation (OPC) to optical communication systems is described.
Abstract: The generation of optical phase-conjugate waves and the application of optical phase conjugation (OPC) to optical communication systems is described. The method of pulse shape distortion compensation by OPC is outlined including distortion due to both fiber dispersion and the optical Kerr effect. The generation of a forward-going phase-conjugate wave in a third-order nonlinear medium is discussed and that by a nondegenerate forward four-wave mixing in a zero-dispersion single-mode fiber (SMF) is investigated. Suppressing the stimulated Brillouin scattering (SBS) of a pump wave in the fiber prevents saturation of the generation efficiency of the phase-conjugate wave even when the pump power exceeds the SBS threshold. In transmission experiments through a 200-km standard SMF with a 16-Gb/s intensity-modulated signal and a 5-Gb/s continuous-phase FSK (CPFSK) modulated signal, it is shown the applicability of OPC is modulation independent and that OPC effectively compensates for both chromatic dispersion and the optical Kerr effect. >
TL;DR: It is established that the noise, which initiates this process and dominates the emission near the SBS threshold, is dramatically suppressed from the onset of strong SBS emission, giving rise to various highly deterministic dynamical features.
Abstract: We report the observation and characterization of chaos in stimulated Brillouin scattering (SBS) generated in a single-mode fiber in the presence of weak external feedback. We establish that the noise, which initiates this process and dominates the emission near the SBS threshold, is dramatically suppressed from the onset of strong SBS emission, giving rise to various highly deterministic dynamical features.
TL;DR: In this article, a high resolution spectral analysis of the emission of a stimulated Brillouin scattering fiber ring laser was performed, demonstrating the single frequency operation of such lasers and a 3 Hz emission linewidth.
Abstract: A high resolution spectral analysis of the emission of a stimulated Brillouin scattering fibre ring laser has been performed, demonstrating the single frequency operation of such lasers and a 3 Hz emission linewidth.
TL;DR: In this paper, a non-degenerate forward four-wave mixing in a singlemode fiber was achieved by suppressing the stimulated Brillouin scattering of pump light at a pump power of +17 dBm with an associated internal parametric gain of 3.3 dB.
Abstract: Highly efficient nondegenerate forward four-wave mixing in a singlemode fibre was achieved by suppressing the stimulated Brillouin scattering of pump light. A conversion efficiency of -4.6 dB, including a fibre loss of 5.3 dB, was obtained at a pump power of +17 dBm with an associated internal parametric gain of 3.3 dB.
TL;DR: In this article, the frequency pulling effect caused by the nonlinear phase shift associated with stimulated Brillouin scattering (SBS) was investigated in detail both theoretically and experimentally.
Abstract: The lasing frequencies of a Brillouin fiber ring laser are shifted slightly from the resonant frequencies of the cold fiber ring resonator due to the optical Kerr effect and the nonlinear phase shift associated with stimulated Brillouin scattering (SBS) used as the gain mechanism in this type of laser. These frequency pulling effects are investigated in detail both theoretically and experimentally. The results of this study are useful in many Brillouin fiber ring laser applications such as Brillouin fiber optic gyroscopes, microwave generators, and frequency shifters. To the authors' knowledge this is the first time the frequency pulling effect caused by the nonlinear phase shift associated with SBS is reported. >
TL;DR: The saturation magnetization of the alloys was measured independently through superconducting quantum interference device magnetometry as mentioned in this paper, and the magnetic field dependence of the spin wave spectrum as well as the inplane directional dependence of surface magnon were determined.
Abstract: Brillouin scattering measurements from several bcc Fe1−xCox epitaxial films are reported. The magnetic‐field dependence of the spin‐wave spectrum as well as the in‐plane directional dependence of the surface magnon are determined. The saturation magnetization of the alloys was measured independently through superconducting quantum interference device magnetometry. Self‐consistent fitting of the magnon dispersions determined from the separate Brillouin experiments provide values for the concentration dependence of the exchange stiffness D, the fourth‐order crystalline cubic anisotropy K1, and surface anisotropies Ks and Ks,p. In agreement with ferromagnetic resonance data, K1 is found to change sign for x beyond about 35 at. % while D steadily increases with cobalt concentration up to x∼0.5 and subsequently decreases in two Co‐rich samples.
TL;DR: In this article, the authors performed extensive bidirectional system experiments to investigate the crosstalk from Brillouin scattering in more detail, including its polarization properties, and they found that for high powers most of the energy is backscattered to a 11 GHz lower frequency.
Abstract: In case of a large number of channels and a limited available optical bandwidth (limited laser tuning range) it may be necessary to chose a channel spacing near 0 or 11 GHz, where Rayleigh-and Brillouin backscattering introduce crosstalk in a bidirectional system. Although there is much literature on stimulated Brillouin scattering, that occurs at high powers, there is hardly any attention paid to what happens at relatively low input powers. Furthermore there are no system measurements which thoroughly investigate these effects. The authors performed extensive bidirectional system experiments to investigate the crosstalk from Brillouin scattering in more detail, including its polarization properties. They found, that, while for high powers most of the energy is backscattered to a 11 GHz lower frequency, for low powers there is no difference for the crosstalks at 11 GHz higher or 11 GHz lower than the signal frequency. The power budget is limited to 40 dB for both cases. The predicted 33.3% degree of polarization of low-power Brillouin scattering is experimentally confirmed for the first time. >
TL;DR: In this paper, a qualitative understanding of the time dependence of stimulated Brillouin scattering (SBS) provides estimates of the amount of temporal growth that occurs in current inertial confinement fusion and short laser pulse interaction experiments when the growth is limited by the length of the experiment or by motion of the hot spots induced by beam smoothing.
Abstract: A qualitative understanding of the time dependence of stimulated Brillouin scattering (SBS) provides estimates of the amount of temporal growth that occurs in current inertial confinement fusion and short laser pulse interaction experiments when the growth is limited by the length of the experiment or by motion of the ‘‘hot spots’’ of the laser intensity pattern induced by beam smoothing. In the weak coupling limit, the instantaneous growth rate depends upon the plasma initial conditions early in time, is proportional to t−1/2 later in time, and asymptotically approaches the absolute growth rate (in the absence of damping). When the instability is strongly coupled, the growth rate depends upon the plasma initial conditions early in time but is proportional to t−1/3 later in time. When the growth rate drops to a value comparable to that of the ion acoustic frequency, the instability becomes effectively weakly coupled. The effects of damping are also discussed.
Book•
01 Mar 1994
TL;DR: Optical phase conjugation as mentioned in this paper provides an introduction to the subject as well as an up-to-date account of the latest developments and applications, including nonlinear optical methods and materials used to obtain phase-conjugate reflectors.
Abstract: "Optical Phase Conjugation" provides an introduction to the subject as well as an up-to-date account of the latest developments and applications. The nonlinear optical methods and materials used to obtain phase-conjugate reflectors are discussed in detail by several authors. In particular the processes of degenerate four-wave mixing, stimulated Brillouin scattering and Brillouin-enhanced four-wave mixing are discussed in depth. The properties and theoretical modelling of photorefractive materials, the most important class of materials used to produce conjugate reflectors, are described at length.
TL;DR: In this paper, the authors show that the phonon peaks have Fano-like lineshapes, indicating a strong coupling between them and the broad feature, and lead to elastic constants that differ considerably from ultrasonic values.
TL;DR: In this paper, a (3+3)-pass vernier tandem Fabry-Perot interferometer was constructed to study the elastic and magnetic properties of metallic multilayers by Brillouin scattering.
Abstract: In order to study the elastic and magnetic properties of metallic multilayers by Brillouin scattering, we have constructed a (3+3)-pass vernier tandem Fabry-Perot interferometer. We have also developed master/slave and time-sharing techniques and electronics to stabilize the interferometer during a long spectrum accumulation period of over several hours. In this report, we describe the details of the tandem spectrometer and the control techniques. As an application of the tandem spectrometer, we have studied sound velocity of Rayleigh surface waves existing in Ag/Cu multilayers as a function of the multilayer period. We have observed considerable softening of more than 20% of the surface velocity as the multilayer period decreases from 150 A to 7 A.
TL;DR: A phenomenological description of the amorphization process based upon the behaviour of the acoustic properties, taking into account competition between crystalline and amorphous character, thermally activated structural relaxation and change of symmetry of the crystalline part during irradiation, is given in this paper.
Abstract: Brillouin scattering has been used to measure the acoustic velocity and attenuation of hypersonic wave for neutron-irradiated quartz crystals. Velocity and attenuation show a maximum value as a function of neutron dose. This maximum is interpreted as a transition between two regions. For neutron doses below this maximum, irradiated quartz remains essentially crystalline, while the amorphous character is dominant above the maximum. This picture is in accord with older results derived from annealing studies. A phenomenological description of the amorphization process based upon the behaviour of the acoustic properties, taking into account competition between crystalline and amorphous character, thermally activated structural relaxation and change of symmetry of the crystalline part during irradiation, is given.
TL;DR: In this article, a stimulated Brillouin gain (SBG) spectrometer based on low power continuous-wave frequency-stabilized lasers is described, and the high resolution and broad tuning range of the SBG spectrum of glycerol in the glassy state (T=146 K) is demonstrated using SBG spectra of liquid methylene chloride as an example.
Abstract: We describe a stimulated Brillouin gain (SBG) spectrometer based on low power continuous‐wave frequency‐stabilized lasers. The high resolution and broad tuning range of this spectrometer are demonstrated through a SBG spectrum of glycerol in the glassy state (T=146 K). The narrow Brillouin linewidth (17 MHz half‐width at half‐maximum) and large Brillouin shift (17.31 GHz) in this spectrum illustrate the extremely high equivalent ‘‘finesse’’ of the instrument, a finesse that would be difficult to achieve through interferometric techniques. The accuracy and precision with which the Brillouin shift can be measured are demonstrated using SBG spectra of liquid methylene chloride as an example. Our Brillouin shift values obtained over the temperature range 178–300 K are in excellent agreement with values measured previously by others using spontaneous and stimulated Brillouin scattering.
TL;DR: In this article, a Brillouin scattering study of the product resulting from laser irradiation of C 60 single crystal was performed and a new structure was formed; the acoustic properties of this material are different from pristine solid C 60 and are similar to those of slow polymers or highly porous materials such as carbon aerogels.
TL;DR: The guided-acoustic-wave Brillouin scattering spectra in PANDA fibers in the low-frequency region are unambiguously confirmed with this scheme of symmetric and asymmetric fiber loop mirrors.
Abstract: A new scheme of symmetric and asymmetric fiber loop mirrors is proposed to identify clearly the polarized guided-acoustic-wave Brillouin scattering spectra with multimode laser sources. The guided-acoustic-wave Brillouin scattering spectra in PANDA fibers in the low-frequency region are unambiguously confirmed with this scheme.