Abstract

A novel BOTDA technique for distributed sensing of the Brillouin frequency in optical fibers with cm-order spatial resolution is proposed. The technique is based upon a simple modulation scheme, requiring only a single long pump pulse for acoustic excitation, and no subsequent interrogating pulse. Instead, the desired spatial mapping of the Brillouin response is extracted by taking the derivative of the probe signal. As a result, the spatial resolution is limited by the fall-time of the pump modulation, and the phenomena of secondary “echo” signals, typically appearing in BOTDA sensing methods based upon pre-excitation, is mitigated. Experimental demonstration of the detection of a Brillouin frequency variation significantly smaller than the natural Brillouin linewidth, with a 2cm spatial resolution, is presented.

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References

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  1. L. Zou, X. Bao, Y. Wan, and L. Chen, “Coherent probe-pump-based Brillouin sensor for centimeter-crack detection,” Opt. Lett. 30(4), 370–372 (2005).
    [CrossRef] [PubMed]
  2. A. W. Brown, B. G. Colpitts, and K. Brown, “Dark-pulse Brillouin optical time-domain sensor with 20-mm spatial resolution,” J. Lightwave Technol. 25(1), 381–386 (2007).
    [CrossRef]
  3. Y. Koyamada, Y. Sakairi, N. Takeuchi, and S. Adachi, “Novel technique to improve spatial resolution in Brillouin optical time-domain reflectometry,” IEEE Photon. Technol. Lett. 19(23), 1910–1912 (2007).
    [CrossRef]
  4. L. Thévenaz and S. F. Mafang, “Distributed fiber sensing using Brillouin echoes,” Proc. SPIE 7004, 1–4 (2008).
  5. W. Li, X. Bao, Y. Li, and L. Chen, “Differential pulse-width pair BOTDA for high spatial resolution sensing,” Opt. Express 16, 16–25 (2008).
  6. V. Lecoeuche, D. J. Webb, C. N. Pannell, and D. A. Jackson, “Transient response in high-resolution Brillouin-based distributed sensing using probe pulses shorter than the acoustic relaxation time,” Opt. Lett. 25(3), 156–158 (2000).
    [CrossRef]
  7. H. Naruse and M. Tateda, “Trade-off between the spatial and the frequency resolutions in measuring the power spectrum of the Brillouin backscattered light in an optical fiber,” Appl. Opt. 38(31), 6516–6521 (1999).
    [CrossRef]
  8. R. W. Boyd, Nonlinear Optics, 2nd. ed.(Academic Press, 2003), Chap. 9.
  9. M. Nikles, L. Thévenaz, and P. A. Robert, “Brillouin gain spectrum characterization in single-mode optical fibers,” J. Lightwave Technol. 15(10), 1842–1851 (1997).
    [CrossRef]

2008 (2)

L. Thévenaz and S. F. Mafang, “Distributed fiber sensing using Brillouin echoes,” Proc. SPIE 7004, 1–4 (2008).

W. Li, X. Bao, Y. Li, and L. Chen, “Differential pulse-width pair BOTDA for high spatial resolution sensing,” Opt. Express 16, 16–25 (2008).

2007 (2)

A. W. Brown, B. G. Colpitts, and K. Brown, “Dark-pulse Brillouin optical time-domain sensor with 20-mm spatial resolution,” J. Lightwave Technol. 25(1), 381–386 (2007).
[CrossRef]

Y. Koyamada, Y. Sakairi, N. Takeuchi, and S. Adachi, “Novel technique to improve spatial resolution in Brillouin optical time-domain reflectometry,” IEEE Photon. Technol. Lett. 19(23), 1910–1912 (2007).
[CrossRef]

2005 (1)

2000 (1)

1999 (1)

1997 (1)

M. Nikles, L. Thévenaz, and P. A. Robert, “Brillouin gain spectrum characterization in single-mode optical fibers,” J. Lightwave Technol. 15(10), 1842–1851 (1997).
[CrossRef]

Adachi, S.

Y. Koyamada, Y. Sakairi, N. Takeuchi, and S. Adachi, “Novel technique to improve spatial resolution in Brillouin optical time-domain reflectometry,” IEEE Photon. Technol. Lett. 19(23), 1910–1912 (2007).
[CrossRef]

Bao, X.

W. Li, X. Bao, Y. Li, and L. Chen, “Differential pulse-width pair BOTDA for high spatial resolution sensing,” Opt. Express 16, 16–25 (2008).

L. Zou, X. Bao, Y. Wan, and L. Chen, “Coherent probe-pump-based Brillouin sensor for centimeter-crack detection,” Opt. Lett. 30(4), 370–372 (2005).
[CrossRef] [PubMed]

Brown, A. W.

Brown, K.

Chen, L.

W. Li, X. Bao, Y. Li, and L. Chen, “Differential pulse-width pair BOTDA for high spatial resolution sensing,” Opt. Express 16, 16–25 (2008).

L. Zou, X. Bao, Y. Wan, and L. Chen, “Coherent probe-pump-based Brillouin sensor for centimeter-crack detection,” Opt. Lett. 30(4), 370–372 (2005).
[CrossRef] [PubMed]

Colpitts, B. G.

Jackson, D. A.

Koyamada, Y.

Y. Koyamada, Y. Sakairi, N. Takeuchi, and S. Adachi, “Novel technique to improve spatial resolution in Brillouin optical time-domain reflectometry,” IEEE Photon. Technol. Lett. 19(23), 1910–1912 (2007).
[CrossRef]

Lecoeuche, V.

Li, W.

W. Li, X. Bao, Y. Li, and L. Chen, “Differential pulse-width pair BOTDA for high spatial resolution sensing,” Opt. Express 16, 16–25 (2008).

Li, Y.

W. Li, X. Bao, Y. Li, and L. Chen, “Differential pulse-width pair BOTDA for high spatial resolution sensing,” Opt. Express 16, 16–25 (2008).

Mafang, S. F.

L. Thévenaz and S. F. Mafang, “Distributed fiber sensing using Brillouin echoes,” Proc. SPIE 7004, 1–4 (2008).

Naruse, H.

Nikles, M.

M. Nikles, L. Thévenaz, and P. A. Robert, “Brillouin gain spectrum characterization in single-mode optical fibers,” J. Lightwave Technol. 15(10), 1842–1851 (1997).
[CrossRef]

Pannell, C. N.

Robert, P. A.

M. Nikles, L. Thévenaz, and P. A. Robert, “Brillouin gain spectrum characterization in single-mode optical fibers,” J. Lightwave Technol. 15(10), 1842–1851 (1997).
[CrossRef]

Sakairi, Y.

Y. Koyamada, Y. Sakairi, N. Takeuchi, and S. Adachi, “Novel technique to improve spatial resolution in Brillouin optical time-domain reflectometry,” IEEE Photon. Technol. Lett. 19(23), 1910–1912 (2007).
[CrossRef]

Takeuchi, N.

Y. Koyamada, Y. Sakairi, N. Takeuchi, and S. Adachi, “Novel technique to improve spatial resolution in Brillouin optical time-domain reflectometry,” IEEE Photon. Technol. Lett. 19(23), 1910–1912 (2007).
[CrossRef]

Tateda, M.

Thévenaz, L.

L. Thévenaz and S. F. Mafang, “Distributed fiber sensing using Brillouin echoes,” Proc. SPIE 7004, 1–4 (2008).

M. Nikles, L. Thévenaz, and P. A. Robert, “Brillouin gain spectrum characterization in single-mode optical fibers,” J. Lightwave Technol. 15(10), 1842–1851 (1997).
[CrossRef]

Wan, Y.

Webb, D. J.

Zou, L.

Appl. Opt. (1)

IEEE Photon. Technol. Lett. (1)

Y. Koyamada, Y. Sakairi, N. Takeuchi, and S. Adachi, “Novel technique to improve spatial resolution in Brillouin optical time-domain reflectometry,” IEEE Photon. Technol. Lett. 19(23), 1910–1912 (2007).
[CrossRef]

J. Lightwave Technol. (2)

A. W. Brown, B. G. Colpitts, and K. Brown, “Dark-pulse Brillouin optical time-domain sensor with 20-mm spatial resolution,” J. Lightwave Technol. 25(1), 381–386 (2007).
[CrossRef]

M. Nikles, L. Thévenaz, and P. A. Robert, “Brillouin gain spectrum characterization in single-mode optical fibers,” J. Lightwave Technol. 15(10), 1842–1851 (1997).
[CrossRef]

Opt. Express (1)

W. Li, X. Bao, Y. Li, and L. Chen, “Differential pulse-width pair BOTDA for high spatial resolution sensing,” Opt. Express 16, 16–25 (2008).

Opt. Lett. (2)

Proc. SPIE (1)

L. Thévenaz and S. F. Mafang, “Distributed fiber sensing using Brillouin echoes,” Proc. SPIE 7004, 1–4 (2008).

Other (1)

R. W. Boyd, Nonlinear Optics, 2nd. ed.(Academic Press, 2003), Chap. 9.

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Figures (5)

Fig. 1
Fig. 1

Schematic illustration of the SBS gain profiles experienced by the probe light, for: (a) pump power exists along the entire length of the fiber, and (b) pump power drops to zero in the last section of fiber only. The gain which occurred along this section in situation (a) is detected in situation (b) as the difference dP.

Fig. 2
Fig. 2

Simulated Brillouin Gain mapping, vs. location and frequency, for: (top) the proposed GPT method, (bottom) the referenced dark pulse method. The frequency axis is plotted relative to the background fiber, so that at zero frequency detuning, the SBS response of the background fiber is maximum. On the left side full mappings are illustrated, indicated by color axis (in arbitrary units). On the right are cross-sections of these mappings taken at two exemplary locations – one at the offset fiber section, and one located outside this section. The dotted lines at the top right figure show the Brillouin response obtained by the GPT method at the same locations with a pump modulation having a finite extinction ratio of 15dB.

Fig. 3
Fig. 3

Experimental setup. Both MZMs (Mach-Zehnder Modulators) are amplitude modulators. PC stands for Polarization Controller, EDFA for Erbium-Doped Fiber Amplifier, FBG for Fiber Bragg Grating.

Fig. 4
Fig. 4

Processed experimental data for the case of a 5cm offset segment. Top left – fiber traces as acquired by the oscilloscope, prior to any processing. The dashed lines mark the offset segment in the fiber. Top right – Brillouin gain mapping obtained by trace differentiation, indicated by color axis (in arbitrary units). The frequency shift step size is 0.5MHz. Bottom left – spectral gain curves obtained by taking cross-sections of the gain mapping at exemplary locations. Bottom right - final results, obtained by estimating per each location point the center of the spectral gain-curve. Each point represents 0.5cm of fiber.

Fig. 5
Fig. 5

Processed experimental data for the case of a 2cm offset segment. Left - Brillouin gain mapping obtained by trace differentiation, indicated by color axis (in arbitrary units). The frequency shift step size is 2.5MHz. Right - final results, obtained by estimating per each location point the center of the spectral gain-curve. Each point represents 0.5cm of fiber.

Equations (8)

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E p z 1 v g E p t = j γ e ω p 4 ρ 0 n c E s ρ α E p
E s z + 1 v g E s t = j γ e ω s 4 ρ 0 n c E p ρ * α E s
ρ t + [ Γ B 2 j ( Ω B ω p + ω s ) ] ρ = j γ e Ω B 8 π v a 2 E p E s *
d P s ( z ) d z = G I p P s ( z )         w h e r e         G ( z , ω p ω s ) = γ e 2 ω s 2 n c 3 v a ρ 0 Γ B ( Γ B / 2 ) 2 ( Ω B ω p + ω s ) 2 + ( Γ B / 2 ) 2
P s ( z ) = P s 0 exp [ 0 z I p G ( z ' ) d z ' ]
P detected ( t > t 0 ) = P s 0 exp [ I p 0 L ( v g t / 2 ) G ( z ' ) d z ' ]
d [ ln ( P detected ) ] d t = ( v g I p 2 ) G ( L v g 2 t )         G ( L v g 2 t )
Δ z resolvable = ( v g / 2 ) t fall

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