raman in fiber

Topics: Laser, Raman scattering, Fiber laser Pages: 26 (487 words) Published: May 27, 2014
Raman Amplifier
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

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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
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Basic Raman Concept

Raman scattering from molecular vibration
Brillouin scattering from sound wave: Brillouin Amplifier
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Basic Raman Concept

Spontaneous process: linear
Stimulated process: Raman laser
Coherent anti-Stokes scattering: Raman amplifier
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Basic Raman Concept

Raman Spectrum from SiO2 fiber
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Basic Raman Concept

Need high power laser
Need large Raman cross section
GeO2 Germania: Large Raman cross-section, refractive index
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Raman Fiber Laser

Higher-order Raman spectrum
Laser source: Raman fiber laser
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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
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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
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Raman Fiber Laser
How Does Cascaded Raman Laser Work
Raman Stokes
Stimulated Raman Scattering
Four Wave Mixing
Easy phase matching

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Raman Amplifier

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Raman Amplifier

Coherent anti-Stokes Scattering
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Raman Amplifier

Phase Matching
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Raman Amplifier

Amplifier Gain
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Raman Amplifier

Wide bandwidth Raman amplifier can be realized using
multiple pumps
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Raman Amplifier

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Raman Amplifier

Lossless transmission by Raman amplifier
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Raman Amplifier

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

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Raman Amplifier

Multistage Amplifier
Counter propagating pump
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EDFA+Raman

Combined Raman and EDFA transmission Experiment:
DWDM (Lucent)
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EDFA+Raman

Wide band amplification is possible by dividing into subbands (Lucent) January 8, 2008

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EDFA+Raman

Gain-flattened EDFA+Raman ( Japan)
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EDFA+Raman

Gain-flattened EDFA+Raman ( Japan)
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EDFA+Raman

Gain-flattened EDFA+Raman (Japan)
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Conclusions
High-power laser sources are available by Raman process
itself.
200 to 400 nm Bandwidth Amplifiers are possible
Raman, EDFA combination
Flat gain for WDM
New fiber lasers and gratings make it practical
System with Terabits of capacity are possible

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References
Optical Fiber Telecommunications, Ivan P. Kaminow (1997)
Optical Amplifier and Their...

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
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