## Brillouin scattering gain bandwidth reduction down to 3.4MHz |

Optics Express, Vol. 19, Issue 9, pp. 8565-8570 (2011)

http://dx.doi.org/10.1364/OE.19.008565

Acrobat PDF (890 KB)

### Abstract

We present a simple method for the stimulated Brillouin scattering (SBS) gain bandwidth reduction in an optical fiber. We were able to reduce the natural bandwidth of 20MHz to around 3.4MHz by a superposition of the gain with two losses produced by the same source. This reduced bandwidth can drastically enhance the performance of many different applications which up to now were limited by the minimum of the natural SBS bandwidth.

© 2011 OSA

## 1. Introduction

1. E. P. Ippen and R. H. Stolen, “Stimulated Brillouin scattering in optical fibers,” Appl. Phys. Lett. **21**, 539–540 (1972). [CrossRef]

2. T. Schneider, “Wavelength and line width measurement of optical sources with femtometre resolution,” Electron. Lett. **41**, 1234–1235 (2005). [CrossRef]

3. J. M. S. Domingo, J. Pelayo, F. Villuendas, C. D. Heras, and E. Pellejer, “Very high resolution optical spectrometry by stimulated Brillouin scattering,” IEEE Photon. Technol. Lett. **17**, 855–857 (2005). [CrossRef]

4. S. Preußler, K. Jamshidi, A. Wiatrek, R. Henker, C. Bunge, and T. Schneider, “Quasi-light-storage based on time-frequency coherence,” Opt. Express **17**, 15790–15798 (2009). [CrossRef] [PubMed]

5. T. Schneider, K. Jamshidi, and S. Preußler, “Quasi-Light Storage: A method for the tunable storage of optical packets with a potential delay-bandwidth product of several thousand bits,” J. Lightwave Technol. **28**, 2586–2592 (2010). [CrossRef]

6. A. R. Chraplyvy and R. W. Tkach, “Narrowband tunable optical filter for channel selection in densely packed WDM systems,” Electron. Lett. **22**, 1084–1085 (1986). [CrossRef]

8. A. Loayssa and J. Capmany, “Incoherent microwave photonic filters with complex coefficients using stimulated brillouin scattering,” in *Optical Fiber Communication Conference and Exposition and The National Fiber Optic Engineers Conference, Technical Digest (CD)* (Optical Society of America, 2006), paper OFB2. [CrossRef]

9. X. S. Yao, “Brillouin selective sideband amplification of microwave photonic signals,” IEEE Photon. Technol. Lett. **10**, 138–140 (1998). [CrossRef]

11. A. Yeniay, J. Delavaux, and J. Toulouse, “Spontaneous and stimulated Brillouin scattering gain spectra in optical fibers,” J. Lightwave Technol. **20**, 1425–1432 (2002). [CrossRef]

13. A. Fotiadi, R. Kiyan, O. Deparis, P. Mgret, and M. Blondel, “Statistical properties of stimulated Brillouin scattering in single-mode optical fibers above threshold,” Opt. Lett. **27**, 83–85 (2002). [CrossRef]

## 2. Theory

14. T. Schneider, R. Henker, K. Lauterbach, and M. Junker, “Distortion reduction in Slow Light systems based on stimulated Brillouin scattering,” Opt. Express **16**, 8280–8285 (2008). [CrossRef] [PubMed]

*g*

_{0}is the maximum gain,

*g*

_{1}is the maximum loss,

*γ*

_{0}is the half width at half maximum bandwidth of the Brillouin gain and

*δ*is the separation between the losses. By normalizing Eq. (1) with

14. T. Schneider, R. Henker, K. Lauterbach, and M. Junker, “Distortion reduction in Slow Light systems based on stimulated Brillouin scattering,” Opt. Express **16**, 8280–8285 (2008). [CrossRef] [PubMed]

*δ*of the losses and the ratio

*m*between gain and losses, the overall gain bandwidth can be narrowed. The dependence of the reduced gain bandwidth, normalized to the natural gain versus the loss separation can be seen in Fig. 1(a) for 19 different ratios between gain and loss. The parameter

*m*goes from 0.1 to 1 in steps of 0.05. As can be seen, the gain bandwidth can be narrowed to 50% (Point 1), 20% (Point 2) or even below. This narrowing comes at the cost of a lower gain, as can be seen from Fig. 1(b).

15. T. Schneider, “Time delay limits of stimulated-Brillouin-scattering-based slow light systems,” Opt. Lett. **33**, 1398–1400 (2008). [CrossRef] [PubMed]

*g*is the peak value of the SBS gain coefficient,

_{p}*P*is the input pump power, and

_{p}*L*and

_{eff}*A*are the effective length and area of the fiber. According to [16

_{eff}16. C. C. Lee and S. Chi, “Measurement of stimulated-Brillouin-scattering threshold for various types of fibers using Brillouin optical-time-domain reflectometer,” IEEE Photon. Technol. Lett. **12**, 672–674 (2000). [CrossRef]

*g*= 19. For Point 1 we have

_{SBSTh}*m*= 0.45 thus, the maximum loss is 45% of the maximum gain. For

*d*= 0.6 the gain is reduced by the losses to 33% of its original value. Thus to achieve the original amplification, the gain has to be enhanced by 3. Therefore to have the same ratio, the losses have to be enhanced by 3 as well. But since the losses are smaller than the gain, the threshold is defined by the gain. So, the amplification can be the same as without losses. For Point 2 the threshold will be defined by the losses. Since the gain is reduced to 5%, it has to be increased by 20 to achieve the same amplification. For the same ratio

*m*the losses have to be increased by 20 as well. Since the losses define the threshold, the maximum amplification of this set up can be 19/20 ≈ 1. However, since the other spectral components are suppressed, this still corresponds to an extraction of narrowband frequency components.

## 3. Experiment and results

*f*, which is 10.855GHz for the used fiber. The two sidebands have a distance of twice the Brillouin shift. Afterwards the signal is splitted via a 3dB coupler. In the upper path the upper sideband is filtered out with a fiber Bragg grating (FBG), so that the lower sideband can be used as the gain pump. In the lower path the upper sideband is used in combination with MZM3 to produce the two losses. MZM3 is driven with a sine wave with a frequency corresponding to the parameter

_{SBS}*δ*in Eq. (1). Afterwards both pump waves, for the gain and the two losses, are independently amplified by an erbium doped fiber amplifier (EDFA) and combined via a coupler. On the left side the setup for scanning the reduced gain can be seen. A fiber laser (Koh) with a line width of 1kHz and a wavelength of 1550nm is modulated via MZM1. The fiber laser is just used for measuring the spectrum of the resulting signal. Therefore, the power of the fiber laser is too low to create a Stokes or Anti-Stokes wave. In order to adapt the fiber laser to the wavelength of LD we modulate the input signal at MZM1 with 8GHz and sweep the modulation frequency ±100MHz in 0.5MHz steps during the scanning process. With MZM2 the reference frequency for the lock in amplifier is modulated to the signal. With a FBG one of the sidebands is filtered out. The other sideband falls in the spectral region where the reduced gain is generated. As propagation medium we used a 20km AllWave fiber (

*L*= 13.38

_{eff}*km*,

*α*= 0.19

*dB/km, A*= 86

_{eff}*μm*

^{2}). The pump waves are coupled into the fiber via a circulator. The backscattered wave is splitted with a 90/10 coupler and then detected with an optical spectrum analyzer (OSA) and a photo diode (PD). The electrical signal from the PD is measured by the Lock In amplifier. For every frequency step the corresponding value for the amplitude is recorded. In comparison to a standard SBS system the complexity of the setup is increased minimally. The additional components are limited to two MZM and filters. If the output power of LD is sufficient, the two EDFAs can be replaced by a tunable coupler which set up the gain/loss ratio

*m*. In the used AllWave fiber we have measured a FWHM gain bandwidth of around 20MHz. For a superposition of gain and losses with the parameters

*m*= 0.45 and

*d*= 0.6 the measured result can be seen in Fig. 4(a). For this measurement the power at the output of the EDFA for the gain was 27dBm and for the losses 23.5dBm. Therefore the gain/loss ratio is

*m*= 0.45. The losses are separated by 12MHz which results in

*d*= 0.6. In accordance with the simulation this corresponds to a gain reduction of 50%. The reduction for the parameters

*m*= 0.55 and

*d*= 0.4 can be seen in Fig. 4(b).

*m*= 0.55 and

*d*= 0.3 can be seen. For these values, a reduction of the bandwidth down to 3.4MHz was achieved. This equals to a reduction of the overall gain to 17% of the original Brillouin gain bandwidth.

## 4. Conclusion

## Acknowledgments

## References and links

1. | E. P. Ippen and R. H. Stolen, “Stimulated Brillouin scattering in optical fibers,” Appl. Phys. Lett. |

2. | T. Schneider, “Wavelength and line width measurement of optical sources with femtometre resolution,” Electron. Lett. |

3. | J. M. S. Domingo, J. Pelayo, F. Villuendas, C. D. Heras, and E. Pellejer, “Very high resolution optical spectrometry by stimulated Brillouin scattering,” IEEE Photon. Technol. Lett. |

4. | S. Preußler, K. Jamshidi, A. Wiatrek, R. Henker, C. Bunge, and T. Schneider, “Quasi-light-storage based on time-frequency coherence,” Opt. Express |

5. | T. Schneider, K. Jamshidi, and S. Preußler, “Quasi-Light Storage: A method for the tunable storage of optical packets with a potential delay-bandwidth product of several thousand bits,” J. Lightwave Technol. |

6. | A. R. Chraplyvy and R. W. Tkach, “Narrowband tunable optical filter for channel selection in densely packed WDM systems,” Electron. Lett. |

7. | T. Tanemura, Y. Takushima, and K. Kikuchi, “Narrowband optical filter, with a variable transmission spectrum, using stimulated Brillouin scattering in optical fiber,” Opt. Lett. |

8. | A. Loayssa and J. Capmany, “Incoherent microwave photonic filters with complex coefficients using stimulated brillouin scattering,” in |

9. | X. S. Yao, “Brillouin selective sideband amplification of microwave photonic signals,” IEEE Photon. Technol. Lett. |

10. | R. Boyd, |

11. | A. Yeniay, J. Delavaux, and J. Toulouse, “Spontaneous and stimulated Brillouin scattering gain spectra in optical fibers,” J. Lightwave Technol. |

12. | R. Esman and K. Williams, “Brillouin scattering: beyond threshold,” in |

13. | A. Fotiadi, R. Kiyan, O. Deparis, P. Mgret, and M. Blondel, “Statistical properties of stimulated Brillouin scattering in single-mode optical fibers above threshold,” Opt. Lett. |

14. | T. Schneider, R. Henker, K. Lauterbach, and M. Junker, “Distortion reduction in Slow Light systems based on stimulated Brillouin scattering,” Opt. Express |

15. | T. Schneider, “Time delay limits of stimulated-Brillouin-scattering-based slow light systems,” Opt. Lett. |

16. | C. C. Lee and S. Chi, “Measurement of stimulated-Brillouin-scattering threshold for various types of fibers using Brillouin optical-time-domain reflectometer,” IEEE Photon. Technol. Lett. |

**OCIS Codes**

(290.5900) Scattering : Scattering, stimulated Brillouin

**ToC Category:**

Fiber Optics and Optical Communications

**History**

Original Manuscript: February 18, 2011

Revised Manuscript: March 29, 2011

Manuscript Accepted: April 4, 2011

Published: April 18, 2011

**Citation**

Stefan Preußler, Andrzej Wiatrek, Kambiz Jamshidi, and Thomas Schneider, "Brillouin scattering gain bandwidth reduction down to 3.4MHz," Opt. Express **19**, 8565-8570 (2011)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-9-8565

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### References

- E. P. Ippen and R. H. Stolen, “Stimulated Brillouin scattering in optical fibers,” Appl. Phys. Lett. 21, 539–540 (1972). [CrossRef]
- T. Schneider, “Wavelength and line width measurement of optical sources with femtometre resolution,” Electron. Lett. 41, 1234–1235 (2005). [CrossRef]
- J. M. S. Domingo, J. Pelayo, F. Villuendas, C. D. Heras, and E. Pellejer, “Very high resolution optical spectrometry by stimulated Brillouin scattering,” IEEE Photon. Technol. Lett. 17, 855–857 (2005). [CrossRef]
- S. Preußler, K. Jamshidi, A. Wiatrek, R. Henker, C. Bunge, and T. Schneider, “Quasi-light-storage based on time-frequency coherence,” Opt. Express 17, 15790–15798 (2009). [CrossRef] [PubMed]
- T. Schneider, K. Jamshidi, and S. Preußler, “Quasi-Light Storage: A method for the tunable storage of optical packets with a potential delay-bandwidth product of several thousand bits,” J. Lightwave Technol. 28, 2586–2592 (2010). [CrossRef]
- A. R. Chraplyvy and R. W. Tkach, “Narrowband tunable optical filter for channel selection in densely packed WDM systems,” Electron. Lett. 22, 1084–1085 (1986). [CrossRef]
- T. Tanemura, Y. Takushima, and K. Kikuchi, “Narrowband optical filter, with a variable transmission spectrum, using stimulated Brillouin scattering in optical fiber,” Opt. Lett. 27, 1552–1554 (2002). [CrossRef]
- A. Loayssa and J. Capmany, “Incoherent microwave photonic filters with complex coefficients using stimulated brillouin scattering,” in Optical Fiber Communication Conference and Exposition and The National Fiber Optic Engineers Conference, Technical Digest (CD) (Optical Society of America, 2006), paper OFB2. [CrossRef]
- X. S. Yao, “Brillouin selective sideband amplification of microwave photonic signals,” IEEE Photon. Technol. Lett. 10, 138–140 (1998). [CrossRef]
- R. Boyd, Nonlinear Optics (Academic Press, 2003).
- A. Yeniay, J. Delavaux, and J. Toulouse, “Spontaneous and stimulated Brillouin scattering gain spectra in optical fibers,” J. Lightwave Technol. 20, 1425–1432 (2002). [CrossRef]
- R. Esman and K. Williams, “Brillouin scattering: beyond threshold,” in Optical Fiber Communication Conference , Vol. 2 of 1996 OSA Technical Digest Series (Optical Society of America, 1996), paper ThF5.
- A. Fotiadi, R. Kiyan, O. Deparis, P. Mgret, and M. Blondel, “Statistical properties of stimulated Brillouin scattering in single-mode optical fibers above threshold,” Opt. Lett. 27, 83–85 (2002). [CrossRef]
- T. Schneider, R. Henker, K. Lauterbach, and M. Junker, “Distortion reduction in Slow Light systems based on stimulated Brillouin scattering,” Opt. Express 16, 8280–8285 (2008). [CrossRef] [PubMed]
- T. Schneider, “Time delay limits of stimulated-Brillouin-scattering-based slow light systems,” Opt. Lett. 33, 1398–1400 (2008). [CrossRef] [PubMed]
- C. C. Lee and S. Chi, “Measurement of stimulated-Brillouin-scattering threshold for various types of fibers using Brillouin optical-time-domain reflectometer,” IEEE Photon. Technol. Lett. 12, 672–674 (2000). [CrossRef]

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