Introduction
Basic Raman Concept
High Power Raman Fiber Lasers
Raman Fiber Amplifier
Combining EDFA and Raman Amplifier
Conclusion
January 8, 2008
Y. Lin: Raman Amplifier
1
Introduction
Raman Amplifier was demonstrated in the 1980s
Unavailability of high-power diode laser pump source
Why do you need it : amplify signals from 1270 to 1670 nm any optical fiber can serve as the amplifying medium
Raman process itself provides high-power laser
Disadvantage: Cross-talk
January 8, 2008
Y. Lin: Raman Amplifier
2
Basic Raman Concept
Raman scattering from molecular vibration
Brillouin scattering from sound wave: Brillouin Amplifier
January 8, 2008
Y. Lin: Raman Amplifier
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Basic Raman Concept
Spontaneous process: linear
Stimulated process: Raman laser
Coherent anti-Stokes scattering: Raman amplifier
January 8, 2008
Y. Lin: Raman Amplifier
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Basic Raman Concept
Raman Spectrum from SiO2 fiber
January 8, 2008
Y. Lin: Raman Amplifier
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Basic Raman Concept
Need high power laser
Need large Raman cross section
GeO2 Germania: Large Raman cross-section, refractive index
January 8, 2008
Y. Lin: Raman Amplifier
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Raman Fiber Laser
Higher-order Raman spectrum
Laser source: Raman fiber laser
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Y. Lin: Raman Amplifier
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Raman Fiber Laser
High power are possible
5 W, 9.2 W diode-pumped Nd3+ cladding-pumped Raman fiber lasers
6.8 W diode-pumped Yb3+ cladding-pumped Raman fiber lasers
January 8, 2008
Y. Lin: Raman Amplifier
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Raman Fiber Laser
High-order Raman scattering
Partially reflecting (20%) fiber grating
Eight 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 January 8, 2008
Y. Lin: Raman Amplifier
9
Raman Fiber Laser
How Does Cascaded Raman Laser Work
Raman Stokes
Stimulated Raman Scattering
Four Wave Mixing
Easy phase
References: Optical Fiber Telecommunications, Ivan P. Kaminow (1997) Optical Amplifier and Their Application, Douglas M. Baney (1998) Waveguide Optoelectronics, J. H. March (1990) January 8, 2008 Y. Lin: Raman Amplifier 26