raman amplifier

January 8, 2008 Y. Lin: Raman Amplifier 1

Raman AmplifierRaman Amplifier

IntroductionBasic Raman ConceptHigh Power Raman Fiber Lasers Raman Fiber AmplifierCombining EDFA and Raman AmplifierConclusion


IntroductionIntroduction

Raman Amplifier was demonstrated in the 1980s Unavailability of high-power diode laser pump sourceWhy do you need it : amplify signals from 1270 to 1670 nmany optical fiber can serve as the amplifying mediumRaman process itself provides high-power laserDisadvantage: Cross-talk


Basic Raman ConceptBasic Raman Concept

Raman scattering from molecular vibrationBrillouin scattering from sound wave: Brillouin Amplifier


Basic Raman ConceptBasic Raman Concept

Spontaneous process: linearStimulated process: Raman laserCoherent anti-Stokes scattering: Raman amplifier


Basic Raman Concept Basic Raman Concept

Raman Spectrum from SiO2 fiber


Basic Raman Concept Basic Raman Concept

Need high power laserNeed large Raman cross sectionGeO2 Germania: Large Raman cross-section, refractive index


Raman Fiber Laser Raman Fiber Laser

Higher-order Raman spectrumLaser source: Raman fiber laser



High power are possible5 W, 9.2 W diode-pumped Nd3+ cladding-pumped Raman fiber lasers 6.8 W diode-pumped Yb3+ cladding-pumped Raman fiber lasers



High-order Raman scatteringPartially reflecting (20%) fiber gratingEight out of ten photons are converted to the output Capable of generating high power light at any wavelength from 1.2 to 1.7 microns



How Does Cascaded Raman Laser Work

Raman Stokes Stimulated Raman Scattering Four Wave MixingEasy phase matching



Coherent anti-Stokes Scattering



Phase Matching



Amplifier Gain



Wide bandwidth Raman amplifier can be realized using multiple pumps


Raman Amplifier Raman Amplifier

Lossless transmission by Raman amplifier



Walk-off due to wavelength mismatch in a pulsed Raman amplifier



Multistage AmplifierCounter propagating pump


EDFA+Raman EDFA+Raman

Combined Raman and EDFA transmission Experiment: DWDM (Lucent)



Wide band amplification is possible by dividing into sub-bands (Lucent)



Gain-flattened EDFA+Raman ( Japan)



Gain-flattened EDFA+Raman (Japan)


Conclusions Conclusions

High-power laser sources are available by Raman process itself.200 to 400 nm Bandwidth Amplifiers are possibleRaman, EDFA combinationFlat gain for WDMNew fiber lasers and gratings make it practicalSystem with Terabits of capacity are possible


ReferencesReferences

Optical Fiber Telecommunications, Ivan P. Kaminow (1997)Optical Amplifier and Their Application, Douglas M. Baney(1998)Waveguide Optoelectronics, J. H. March (1990)

raman amplifier

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