Stimulated Raman Scattering Effect Research Articles

Linear Approximation Method for Minimising SRS Effect in All-Optical WDM Fiber Optic Systems

A novel “Linear Approximation Method (LAM)” has been developed and suggested for the estimation of optical powers to be launched at different wavelength channels to minimise the variation in the system performance at different wavelength channels due to Stimulated Raman Scattering (SRS) in Wavelength Division Multiplexed (WDM) fiber optic systems. A 2000 km long point-to-point all-optical WDM fiber optic link having sixteen channels (each channel has a data rate of 2.5 Gbits/sec) with inter-channel separation of 1nm has been simulated to study the effectiveness of the LAM. The efficiency of LAM has also been examined for different inter-amplifier spacing and different levels of total optical power launched into the simulated system.

Effect of Stimulated Raman Scattering on Spectral Characteristics of Ultranarrow Pulses in a Mode-Locked Solid-State Laser

On the basis of numerical modeling, it is shown that the effect of the higher-order group-velocity dispersion is unable to account for the noticeable Stokes displacement of the generation spectrum in a LiSGaF laser with mode-locking due to self-focusing. The results of calculations indicate the determining influence of stimulated Raman scattering on the spectral characteristics of femtosecond pulses.

Optimal Design of a Long Distance WDM Soliton Communication System with Lumped Amplifiers

The effects of Stimulated Raman Scattering (SRS) and Four-Wave Mixing in a WDM soliton communication system with loss and lumped amplifiers are analyzed. The optimal design schemes are drawn up and several design examples are given in this paper.

Analytical characteristics of stimulated Raman scattering in a multimode fiber obtained with an optical time-domain reflectometer

The nonlinear behavior of stimulated Raman scattering (SRS) in a low-loss optical fiber has been analytically and experimentally investigated by the assumption of certain restraint conditions. As a result, it has been found that the SRS light propagating along the optical fiber is expressed in a simple formula by the introduction of nonlinear parameters, which are experimentally identified and whose maximum value is restricted by the restraint conditions. The parameters, moreover, are available for compensating the SRS intensity in the presence of noninteracting light. Therefore the formula for SRS intensity presented is useful for investigating the SRS effect in a multimode fiber.

Optimisation of wavelength spacing in a WDM transmission system in the presence of fibre nonlinearities

The paper studies the transmission limitation of wavelength division multiplexing (WDM) optical fibre systems using inline optical amplifiers imposed by fibre nonlinearities in the presence of optical amplifier noise and fibre dispersion. Two main nonlinear effects, namely four-wave mixing (FWM) and stimulated Raman scattering (SRS), are considered, with the emphasis on the FWM effect. Detailed analysis is carried out to evaluate the transmission distance limitation as a function of various system parameters such as wavelength channel spacing, number of channels and amplifier spacing. It is found that to maximise the transmission distance, a compromise needs to be made between conflicting requirements of channel spacing when considering the FWM and SRS effects, respectively. Various techniques to reduce the FWM impairments are also discussed.

A computer model of non-dispersion-limited stimulated Raman scattering in optical fiber multiple-channel communications

The development of a computer model for non-dispersion-limited stimulated Raman scattering (SRS) in optical fiber multiple-channel communication systems is reported. The model takes into account the pump depletion due to SRS and the different attenuation coefficients at different wavelengths of operation. It can calculate the SRS effects in any fiber, provided the Raman gain profile for that fiber is known. Thus, the model is general in nature and can be used for a number of problems. It can be used to calculate the output power of all the channels, given the input of every channel and its operating wavelength. It can also be used, at least in principle, to determine the input power level if a desired level of output power is required. Moreover, it can be used to estimate the optical amplification of a signal due to SRS. This is possible because the governing equations for all of these processes are similar and therefore can be solved using the same approach.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance degradation due to stimulated Raman scattering in wavelength-division-multiplexed optical-fibre systems

The effects of stimulated Raman scattering (SRS) on a two-channel wavelength-division-multiplexed optical-fibre communication system are analysed. For both amplitude and angle modulation the most important effect of SRS is increased loss for the short-wavelength channel, which in the worst case limits the maximum usable transmitter power to ∼ 50 mW.

Maximum Measurable Distances for a Single-Mode Optical Fiber Fault Locator Using the Stimulated Raman Scattering (SRS) Effect

Maximum measurable distances for a single-mode optical fiber fault locator using the stimulated Raman scattering effect were calculated. Calculations were carried out on the assumption that the light source is an Nd: YAG laser operating at 1.06 µm and the photo-detector is a germanium avalanche photodiode (Ge-APD). The fist to the seventh Stokes lights can be detected by the Ge-APD. Calculations show that a break can be measured in an up to 165km long ultra-low-loss single-mode fiber.

Spectral power handling capability caused by stimulated Raman scattering effect in silica optical fibers

Spectral characteristics of the stimulated Raman scattering (SRS) in silica fibers was studied for the purpose of obtaining higher power transmission capability in single-mode silica optical fibers. When the input power exceeds a critical input power, which depends on the wavelength, nonlinear transmission loss caused by SRS gives rise to excess loss and signal waveform distortion. The SRS effect is reduced under the condition of sufficiently large spectral loss at the first Stokes wavelength.

Laser-stimulated atomic migration

The effects of stimulated Raman scattering (SRS) and of infrared (IR) absorption on the scattering at defects leading to atomic migration in solids is evaluated in detail for certain systems. \DeltaE/kT \approx \sum u_{ic}^{2}/\langleu_{i}u_{i}\rangle , where \DeltaE is the activation energy, u ic is the many-body critical displacement in a migration event, and \langleu_{i}u_{i}\rangle is the equal-time correlation function including anharmonic terms. Using the equal-time correlation for the defect lattice in the harmonic approximation, we get \DeltaE/kT_{eff} \propto 1/\sum h[2(n_{s} + n_{e}) + 1] where T eff includes both n e and n s the externally and thermally excited phonon numbers, respectively. The phonon rate density required for an observable effect of SRS or IR absorption on diffusion in solids is n_{e}^{(c)}c_{s}/V \approx 10^{26} - 10^{27} phonons/s.cm2, where n_{e}^{(c)} is a critical number of high wave-vector laser-stimulated phonons, c s , is the sound velocity, and V, the volume per atom. In KCI at 110 K, theory shows that n_{e} = 0.2 can produce a factor of 10 effect on the reorientation of Na:F A centers. Anharmonic effects on \langleu_{i}u_{i}\rangle were calculated and numerical estimates indicate that they would be experimentally observable for large n e . It is found that some of the effects reported here probably contribute, in part, to the permanent damage tracks caused by high-power laser beams in solids and provide an internal source for the initiation of microcracks. In addition, the direction of the stimulated phonon wave vector is shown to produce a directional effect in the control of atomic migration.

Measurement of Raman Scattering Cross Sections for Use in Calculating Stimulated Raman Scattering Effects

The magnitude of stimulated Raman scattering (SRS) of the Raman laser effect depends upon the peak values of ordinary Raman scattering cross sections just as ordinary laser gain depends upon the peak value of an absorption cross section. We give here the results of the measurements of peak Raman scattering cross section for three Raman lines in nitrobenzene, benzene, and toluene for which SRS has been studied and for two other lines in benzene and toluene from which no observable SRS could be produced. The intensity of SRS calculated from these cross sections agrees with SRS measurements for these substances. A ruby laser was used as the light source. A 2-m grating spectrograph was used as the dispersing element for photometric detection. The scattering was observed at 90° from the incident laser beam and was measured for different polarizations of the incident and scattered light. The peak cross sections were measured by scanning the wavelength in steps.