Simultaneously Stokes and antiStokes Raman amplification in silica fiber

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Simultaneously Stokes and anti-Stokes Raman
amplification in silica fiber
Victor G. Bespalov Russian Research Center "S. I.
Vavilov State Optical Institute"
Nikolai S. Makarov Saint-Petersburg State
Institute of Fine Mechanics and Optics (Technical
University)
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Outline

• The main goal
• Principle of quasi-phase matching
• System of SRS equations
• Properties of quasi-phase matching
• Numerical simulations results
• Conclusions
• References

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EDFA-amplification
- It is necessary to provide amplification with
an error no more than ? 5 dB in the whole
spectral band of the amplifier.
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SRS amplification in silica fiber
- With ?pump1480 nm, due to the broadband of
SRS-amplification ?stokes1550 - 1580 nm.
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Combined EDFA andStokes SRS amplification
- Flattening of amplification curve is possible
with combined using of EDFA and Stokes SRS
amplifier.
- For opening of 1310 nm amplification window we
offer to use simultaneously Stokes and
anti-Stokes quasi-phase matching stimulated Raman
scattering amplification
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Principle of quasi-phase matching
Nonlinearity ?(2)
Nonlinearity ?(3)
Raman active medium
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Principle of quasi-phase matching at SRS
- Generalized phase ?2?p-?a-?s-(kaks-2kp)r, wher
e ki is the wave vector of interacting wave,
that describes the direction of energy conversion
pump Stokes anti-Stokes, on passive layers
input (?0, ?2) and active layers input (?1, ?3)
do not practically change, that in a final result
provides a realization of quasi-phase matching
conditions.
?(3)?0
?(3)0
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System of steady-state SRS equations
? wave mismatching, g steady-state Raman gain
coefficient, ?i frequencies of interacting
waves, Aj complex wave amplitudes.
In this system the waves mismatching and Raman
gain are the functions of coordinate for
nonlinear (?(3)?0) and linear (?(3)0) layers.
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Optimum ratio of input Stokes/pump intensities
- There is an optimum value of input Stokes/pump
waves intensities ratio.
- This dependence can be approximated as
Is/Ip,opt0,1359g-2,6146.
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Comparison of quasi-phase and phase matching
Hydrogen ? 3.84 rad/cm g 3.0 cm/GW 1 -
quasi-phase matching 2 - without (quasi-) phase
matching 3 - phase matching.
- Conversion efficiency at quasi-phase matching
is lower than at phase matching and higher than
at simple focusing in Raman media.
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Critical pump wave intensity
- There is a critical value of pump intensity.
- This dependence can be approximated as
Icr.p0.4?/g.
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SRS in silica fiber
- For amplification in both windows it is
possible to use simultaneously amplification of
Stokes and anti-Stokes radiation at condition of
quasi-phase matching.
- The structure is quasi-periodic.
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SimultaneouslyStokes and anti-Stokes
amplification
- Stokes and anti-Stokes amplification provides
amplification peaks at wavelengths of 1389 and
1583 nm with pump 1480 nm.
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Analytical model ofquasi-phase matching SRS
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Analytical model ofquasi-phase matching SRS
Improvement of calculation rate with constant
calculation accuracy is 120 times
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Calculating losses in silica fiber
- With losses about 0.3 dB/km (characteristic
value for today optical fiber) the amplification
occurs practically in whole medium.
1 - attenuation zone, 2 - amplification zone
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• Conclusion

• Stokes-Anti-Stokes SRS amplification is useful
  for improvement of EDFA amplification curve and
  creating of amplified channel in 1310 nm
  transparency window.
• Layers lengths do not depend on input waves
  intensities if the ratio between
  pump/Stokes/anti-Stokes waves intensities does
  not change.
• The analytical model of quasi-phase matched
  stimulated Raman scattering in silica fiber is
  formulated and the recurrent formulas for layers
  lengths and amplitudes of interacting waves are
  received.
• The analytical model allow significant
  improvement of calculation rate with same
  accuracy.
• The obtained results are promising for the
  development of new effective optical amplifiers.

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• References

• G. Randy, L. I. Tingyc, "Optical amplifiers
  transform long distance lightvoice
  telecommunications", Proc. IEEE, 84, pp.
  870-883, 1996.
• P. Urquhart, "Review of rare-earth-doped fiber
  lasers amplifiers", IEE Proc, 6, 385-407, 1988.
• M. H. Ahmed, M. Shalaby, F. M. Misk, "Combined
  erbium and Raman amplification at 1.55 ?m in
  submarine links using backward pumping at 1.48
  ?m", Pure Appl. Opt., 7, 659-666, 1998.
• V. G. Bespalov, N. S. Makarov, "Quasi-phase
  matching anti-Stokes SRS generation", Proc. SPIE,
  vol. 4268, 2001, pp. 109-116.
• J. J. Ottusch, M. S. Mangir, D. A. Rockwell,
  "Efficient anti-Stokes Raman conversion by
  four-wave mixing in gases", J. Opt. Soc. Am. B 8,
  pp. 68-77, 1991.

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