Abstract

Subpeaks in the Brillouin loss spectra of distributed fiber-optic sensors were observed for what is believed to be the first time and studied. We discovered that the Fourier spectrum of the pulsed signal and the off-resonance oscillation both contributed to subpeaks. The off-resonance oscillation at frequency ννB is the oscillation in the Brillouin time domain when beat frequency ν of the two counterpropagating laser beams does not match local Brillouin frequency νB. This study is important in differentiating the subpeaks from actual strain–temperature peaks.

© 2005 Optical Society of America

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References

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  1. X. Bao, J. Dhliwayo, N. Heron, D. J. Webb, and D. A. Jackson, J. Low Temp. Phys. 13, 1340 (1995).
  2. X. Bao, D. J. Webb, and D. A. Jackson, Electron. Lett. 29, 976 (1993).
    [CrossRef]
  3. S. Afshar V., G. A. Ferrier, X. Bao, and L. Chen, Opt. Lett. 28, 1418 (2003).
    [CrossRef]
  4. A. W. Brown, “Development of a Brillouin scattering based distributed fibre optic strain sensor,” Ph.D. dissertation (Department of Physics, University of New Brunswick, Fredericton, New Brunswick, Canada, 2000).
  5. R. Chu, M. Kanefsky, and J. Falk, J. Appl. Phys. 71, 4653 (1992).
    [CrossRef]

2003

1995

X. Bao, J. Dhliwayo, N. Heron, D. J. Webb, and D. A. Jackson, J. Low Temp. Phys. 13, 1340 (1995).

1993

X. Bao, D. J. Webb, and D. A. Jackson, Electron. Lett. 29, 976 (1993).
[CrossRef]

1992

R. Chu, M. Kanefsky, and J. Falk, J. Appl. Phys. 71, 4653 (1992).
[CrossRef]

Afshar V., S.

Bao, X.

S. Afshar V., G. A. Ferrier, X. Bao, and L. Chen, Opt. Lett. 28, 1418 (2003).
[CrossRef]

X. Bao, J. Dhliwayo, N. Heron, D. J. Webb, and D. A. Jackson, J. Low Temp. Phys. 13, 1340 (1995).

X. Bao, D. J. Webb, and D. A. Jackson, Electron. Lett. 29, 976 (1993).
[CrossRef]

Brown, A. W.

A. W. Brown, “Development of a Brillouin scattering based distributed fibre optic strain sensor,” Ph.D. dissertation (Department of Physics, University of New Brunswick, Fredericton, New Brunswick, Canada, 2000).

Chen, L.

Chu, R.

R. Chu, M. Kanefsky, and J. Falk, J. Appl. Phys. 71, 4653 (1992).
[CrossRef]

Dhliwayo, J.

X. Bao, J. Dhliwayo, N. Heron, D. J. Webb, and D. A. Jackson, J. Low Temp. Phys. 13, 1340 (1995).

Falk, J.

R. Chu, M. Kanefsky, and J. Falk, J. Appl. Phys. 71, 4653 (1992).
[CrossRef]

Ferrier, G. A.

Heron, N.

X. Bao, J. Dhliwayo, N. Heron, D. J. Webb, and D. A. Jackson, J. Low Temp. Phys. 13, 1340 (1995).

Jackson, D. A.

X. Bao, J. Dhliwayo, N. Heron, D. J. Webb, and D. A. Jackson, J. Low Temp. Phys. 13, 1340 (1995).

X. Bao, D. J. Webb, and D. A. Jackson, Electron. Lett. 29, 976 (1993).
[CrossRef]

Kanefsky, M.

R. Chu, M. Kanefsky, and J. Falk, J. Appl. Phys. 71, 4653 (1992).
[CrossRef]

Webb, D. J.

X. Bao, J. Dhliwayo, N. Heron, D. J. Webb, and D. A. Jackson, J. Low Temp. Phys. 13, 1340 (1995).

X. Bao, D. J. Webb, and D. A. Jackson, Electron. Lett. 29, 976 (1993).
[CrossRef]

Electron. Lett.

X. Bao, D. J. Webb, and D. A. Jackson, Electron. Lett. 29, 976 (1993).
[CrossRef]

J. Appl. Phys.

R. Chu, M. Kanefsky, and J. Falk, J. Appl. Phys. 71, 4653 (1992).
[CrossRef]

J. Low Temp. Phys.

X. Bao, J. Dhliwayo, N. Heron, D. J. Webb, and D. A. Jackson, J. Low Temp. Phys. 13, 1340 (1995).

Opt. Lett.

Other

A. W. Brown, “Development of a Brillouin scattering based distributed fibre optic strain sensor,” Ph.D. dissertation (Department of Physics, University of New Brunswick, Fredericton, New Brunswick, Canada, 2000).

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Figures (5)

Fig. 1
Fig. 1

(a) Experimental Brillouin spectra for a 2 - ns pulse and different uniform strains. (b) Calculated Brillouin spectrum for a 2 - ns pulse and 6400 - μ ϵ uniform strain. The Brillouin frequencies are translated to zero for comparison.

Fig. 2
Fig. 2

(a) Experimental Brillouin spectrum at the center of a 2 - m fiber for a 10 - ns pulse; the flat top is due to the electrical chop off. (b) Calculated Brillouin spectrum with the same parameters as in (a).

Fig. 3
Fig. 3

Time domains of the cw pump for seven beat frequencies within the neighborhood of 12 585 MHz . Inset, Brillouin spectrum at t = 21 ns (or z = 0.61 m since t 0 = 15 ns for a 1 - m fiber).

Fig. 4
Fig. 4

Competition between the Fourier peaks and the side peaks caused by off-resonance oscillation. Positions of the first two side peaks caused by Fourier transformation are indicated.

Fig. 5
Fig. 5

(a) Brillouin spectra at the fiber center when the fiber is loose with ν B = 12 795 MHz and when it has a 3 - cm strained region with ν B = 12 845 MHz . (b) Spectrum obtained by subtracting the spectrum in the loose case from that in the strained case.

Tables (1)

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Table 1 Effective Region of the Three Terms in Eq. (5)

Equations (9)

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( z 1 v g t 1 2 α ) E p = Q ¯ E s ,
( t 1 v g t + 1 2 α ) E s = Q ¯ * E p ,
( t + Γ ) Q ¯ = 1 2 Γ 1 g B E p E s * ,
E s ( t ) = I in { cos θ exp [ i ϕ ( t ) ] + sin θ exp [ i ϕ ( t ) ] } ,
Q ¯ ( t ) = C 0 t E p ( t ) E s * ( t ) exp ( Γ t ) d t ,
E s ( t ) E dc + E S 0 f ( t , t 0 , τ p ) ,
Q ¯ ( t ) 2 = C 2 [ T 1 2 + 2 Re ( T 1 T 2 * ) + T 2 2 ] ,
T 1 = E dc * 0 t E p ( t ) exp ( Γ t ) d t ,
T 2 = E S 0 * 0 t E p ( t ) exp ( Γ t ) f ( t , t 0 , τ p ) d t .

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