Combined StokesantiStokes Raman amplification in fiber - PowerPoint PPT Presentation

Title: Combined StokesantiStokes Raman amplification in fiber


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Combined Stokes-anti-Stokes Raman amplification
in fiber
Victor G. Bespalov All 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

• Main goals
• Principle of quasi-phase matching
• System of SRS equations
• Properties of quasi-phase matched SRS
• Numerical simulations results for fibers
• 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 improvement of amplification curve and
creating of a new channel in 1310 nm we propose
to use simultaneous Stokes and anti-Stokes SRS
amplification at QPM.
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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
? waves 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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Efficiency of anti-Stokes SRS generation in
Raman-active media
Hydrogen ? 3.84 rad/cm g 3.0 cm/GW.
- There is an optimal ratio Is/Ip, for maximal
conversion efficiency.
- The ratio depended from waves mismatching and
steady-state Raman gain coefficient.
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Energy conversion at quasi-phase matching
Hydrogen ? 3.84 rad/cm g 3.0 cm/GW Is(0)
0.0023 GW/cm2 efficiency ? 30
- At optimum ratio Is/Ip, conversion efficiency
reached more than 30, but Stokes intensity is
higher then anti-Stokes intensity.
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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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Lengths of active and passive zones
- Similar plot can be achieved for barium nitrate.
- Structure of layers is not periodical.
- Lengths of active/passive layers are
monotonously decreased/ increased.
- It is essentially different from quasi-phase
matching in ?(2) media.
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Characteristic zone lengths
- It is possible to approximate this dependence
as La 2.6/? and Lp 3.9/?.
- With increasing of waves mismatching structure
become more periodical.
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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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EDFA and anti-Stokes SRS amplification
- Combined EDFA and simultaneously Stokes and
anti-Stokes amplification provides the
amplification in both windows.
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• Conclusions

• Stokes-Anti-Stokes SRS amplification is useful
  for improvement of EDFA amplification curve and
  creating of amplified channel in 1310 nm
  transparency window.
• Quasi-phase matching structure in silica fibers
  is quasi-periodic.
• Layers lengths do not depend on input waves
  intensities if the ratio between
  pump/Stokes/anti-Stokes waves intensities does
  not change.
• For more effective flattening of the
  amplification curve and broadening of amplified
  channel in 1310 nm transparency window we can use
  pump at several wavelengths.

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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 (accepted for publication).
• J. J. Ottusch, M. S. Mangir, D. A. Rockwell,
  "Efficient anti-Stokes Raman conversion by
  four-wave mixing in gases", J. Opt. Soc. Am., 8,
  pp. 68-77, 1991.