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Simultaneously Stokes and anti-Stokes Raman amplification in silica fiber

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

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Simultaneously Stokes and anti-Stokes Raman amplification in silica fiber

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

  2. Outline • The main goal • Principle of quasi-phase matching • System of SRS equations • Properties of quasi-phase matching • Numerical simulations results • Conclusions • References 2

  3. EDFA-amplification - It is necessary to provide amplification with an error no more than  5 dB in the whole spectral band of the amplifier. 3

  4. SRS amplification in silica fiber - With pump=1480 nm, due to the broadband of SRS-amplification stokes=1550 - 1580 nm. 4

  5. 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 5

  6. Principle of quasi-phase matching Nonlinearity (2) Nonlinearity (3) Raman active medium 6

  7. Principle of quasi-phase matching at SRS -Generalized phase =2p-a-s-(ka+ks-2kp)r, where 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 7

  8. 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. 8

  9. Optimum ratio of input Stokes/pump intensities - There is an optimum value of input Stokes/pump waves intensities ratio. -This dependence can be approximated asIs/Ip,opt=0,1359g-2,6146. 9

  10. 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. 10

  11. Critical pump wave intensity - There is a critical value of pump intensity. -This dependence can be approximated as Icr.p=0.4Δ/g. 11

  12. 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. 12

  13. SimultaneouslyStokes and anti-Stokes amplification - Stokes and anti-Stokes amplification provides amplification peaks at wavelengths of 1389 and 1583 nm with pump 1480 nm. 13

  14. Analytical model ofquasi-phase matching SRS 14

  15. Analytical model ofquasi-phase matching SRS Improvement of calculation rate with constant calculation accuracy is ~120 times 15

  16. 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 16

  17. 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. Conclusion 17

  18. 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. References 18

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