Abstract

All-fiber laser Doppler vibrometer systems have great potential in the application of remote acoustic detection. However, due to the requirement for a long operating distance, a long coherence length laser is required, which can drive the system cost high. In this paper, a system using a short coherence length laser is proposed and demonstrated. Experimental analysis indicates that the multi-longitudinal modes of the laser cause detection noise and that the unequal length between two paths (local oscillator path and transmission path) increases the intensity and the frequency components of the noise. In order to reduce the noise, the optical length of the two paths needs to be balanced, within the coherence length of the source. We demonstrate that adopting a tunable optical delay to compensate the unequal length significantly reduces the noise. In a comparison of the detection results by using a short coherence laser and a long coherence laser, our developed system gives a good performance on the acoustic signal detection from three meters away.

© 2012 Optical Society of America

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References

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  1. Z. Zhu and W. Li, “Integration of laser vibrometer and infrared video for multimedia surveillance display,” CS Dept, CUNY Graduate Center, New York, NY, US (January 13, 2010), TR-2005006, http://tr.cs.gc.cuny.edu/tr/files/TR-2005006.pdf .
  2. Y. Qu, T. Wang, and Z. Zhu, “An active multimodal sensing platform for remote voice detection,” in Proceedings of 2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (IEEE, 2010), pp. 627–632.
  3. F. Branca, F. Bini, and F. Marinozzi, “Optimum choice of acoustic properties of filling materials using optical measurement,” in Proceedings of the 2004 IEEE International Ultrasonics, Ferroelectrics, and Frequency Control Joint 50th Anniversary Conference Vol. 3 (IEEE, 2004), pp. 1663–1665.
  4. L. Antonelli and F. Blackmon, “Experimental demonstration of remote, passive acousto-optic sensing,” J. Acoust. Soc. Am. 116, 3393–3403 (2004).
    [CrossRef]
  5. E. Esposito, S. Copparoni, and B. Naticchia, “Recent progress in diagnostics of civil structures by laser vibrometry,” in Proceedings of the 16th World Conference on Non-destructive Testing (International Committee for Nondestructive Testing, 2004), pp. 713–720.
  6. Polytec Laser Vibrometer, http://www.polytec.com/ .
  7. Ometron, http://www.imageautomation.com/ .
  8. J. Shang, Y. He, and D. Liu, “Laser Doppler vibrometer for real-time speech-signal acquirement,” Chin. Opt. Lett. 7, 732–733 (2009).
    [CrossRef]
  9. P. J. Rodrigo and C. Pedersen, “Reduction of phase-induced intensity noise in a fiber-based coherent Doppler lidar using polarization control,” Opt. Express 18, 5320–5327 (2010).
    [CrossRef]
  10. www.santec.com .
  11. www.npphotonics.com .
  12. www.goochandhousego.com .
  13. L. Richter and H. Mandelberg, “Linewidth determination from self-heterodyne measurements with subcoherence delay times,” IEEE J. Quantum Electron. 22, 2070–2074 (1986).
    [CrossRef]
  14. PI1036, Corning SMF-28 TM Optical Fiber Product information, April 2002.

2010

2009

2004

L. Antonelli and F. Blackmon, “Experimental demonstration of remote, passive acousto-optic sensing,” J. Acoust. Soc. Am. 116, 3393–3403 (2004).
[CrossRef]

1986

L. Richter and H. Mandelberg, “Linewidth determination from self-heterodyne measurements with subcoherence delay times,” IEEE J. Quantum Electron. 22, 2070–2074 (1986).
[CrossRef]

Antonelli, L.

L. Antonelli and F. Blackmon, “Experimental demonstration of remote, passive acousto-optic sensing,” J. Acoust. Soc. Am. 116, 3393–3403 (2004).
[CrossRef]

Bini, F.

F. Branca, F. Bini, and F. Marinozzi, “Optimum choice of acoustic properties of filling materials using optical measurement,” in Proceedings of the 2004 IEEE International Ultrasonics, Ferroelectrics, and Frequency Control Joint 50th Anniversary Conference Vol. 3 (IEEE, 2004), pp. 1663–1665.

Blackmon, F.

L. Antonelli and F. Blackmon, “Experimental demonstration of remote, passive acousto-optic sensing,” J. Acoust. Soc. Am. 116, 3393–3403 (2004).
[CrossRef]

Branca, F.

F. Branca, F. Bini, and F. Marinozzi, “Optimum choice of acoustic properties of filling materials using optical measurement,” in Proceedings of the 2004 IEEE International Ultrasonics, Ferroelectrics, and Frequency Control Joint 50th Anniversary Conference Vol. 3 (IEEE, 2004), pp. 1663–1665.

Copparoni, S.

E. Esposito, S. Copparoni, and B. Naticchia, “Recent progress in diagnostics of civil structures by laser vibrometry,” in Proceedings of the 16th World Conference on Non-destructive Testing (International Committee for Nondestructive Testing, 2004), pp. 713–720.

Esposito, E.

E. Esposito, S. Copparoni, and B. Naticchia, “Recent progress in diagnostics of civil structures by laser vibrometry,” in Proceedings of the 16th World Conference on Non-destructive Testing (International Committee for Nondestructive Testing, 2004), pp. 713–720.

He, Y.

Liu, D.

Mandelberg, H.

L. Richter and H. Mandelberg, “Linewidth determination from self-heterodyne measurements with subcoherence delay times,” IEEE J. Quantum Electron. 22, 2070–2074 (1986).
[CrossRef]

Marinozzi, F.

F. Branca, F. Bini, and F. Marinozzi, “Optimum choice of acoustic properties of filling materials using optical measurement,” in Proceedings of the 2004 IEEE International Ultrasonics, Ferroelectrics, and Frequency Control Joint 50th Anniversary Conference Vol. 3 (IEEE, 2004), pp. 1663–1665.

Naticchia, B.

E. Esposito, S. Copparoni, and B. Naticchia, “Recent progress in diagnostics of civil structures by laser vibrometry,” in Proceedings of the 16th World Conference on Non-destructive Testing (International Committee for Nondestructive Testing, 2004), pp. 713–720.

Pedersen, C.

Qu, Y.

Y. Qu, T. Wang, and Z. Zhu, “An active multimodal sensing platform for remote voice detection,” in Proceedings of 2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (IEEE, 2010), pp. 627–632.

Richter, L.

L. Richter and H. Mandelberg, “Linewidth determination from self-heterodyne measurements with subcoherence delay times,” IEEE J. Quantum Electron. 22, 2070–2074 (1986).
[CrossRef]

Rodrigo, P. J.

Shang, J.

Wang, T.

Y. Qu, T. Wang, and Z. Zhu, “An active multimodal sensing platform for remote voice detection,” in Proceedings of 2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (IEEE, 2010), pp. 627–632.

Zhu, Z.

Y. Qu, T. Wang, and Z. Zhu, “An active multimodal sensing platform for remote voice detection,” in Proceedings of 2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (IEEE, 2010), pp. 627–632.

Chin. Opt. Lett.

IEEE J. Quantum Electron.

L. Richter and H. Mandelberg, “Linewidth determination from self-heterodyne measurements with subcoherence delay times,” IEEE J. Quantum Electron. 22, 2070–2074 (1986).
[CrossRef]

J. Acoust. Soc. Am.

L. Antonelli and F. Blackmon, “Experimental demonstration of remote, passive acousto-optic sensing,” J. Acoust. Soc. Am. 116, 3393–3403 (2004).
[CrossRef]

Opt. Express

Other

www.santec.com .

www.npphotonics.com .

www.goochandhousego.com .

E. Esposito, S. Copparoni, and B. Naticchia, “Recent progress in diagnostics of civil structures by laser vibrometry,” in Proceedings of the 16th World Conference on Non-destructive Testing (International Committee for Nondestructive Testing, 2004), pp. 713–720.

Polytec Laser Vibrometer, http://www.polytec.com/ .

Ometron, http://www.imageautomation.com/ .

PI1036, Corning SMF-28 TM Optical Fiber Product information, April 2002.

Z. Zhu and W. Li, “Integration of laser vibrometer and infrared video for multimedia surveillance display,” CS Dept, CUNY Graduate Center, New York, NY, US (January 13, 2010), TR-2005006, http://tr.cs.gc.cuny.edu/tr/files/TR-2005006.pdf .

Y. Qu, T. Wang, and Z. Zhu, “An active multimodal sensing platform for remote voice detection,” in Proceedings of 2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (IEEE, 2010), pp. 627–632.

F. Branca, F. Bini, and F. Marinozzi, “Optimum choice of acoustic properties of filling materials using optical measurement,” in Proceedings of the 2004 IEEE International Ultrasonics, Ferroelectrics, and Frequency Control Joint 50th Anniversary Conference Vol. 3 (IEEE, 2004), pp. 1663–1665.

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Figures (12)

Fig. 1.
Fig. 1.

Experimental setup of the remote LDV acoustic detection system.

Fig. 2.
Fig. 2.

Simplified system with equal lengths of two paths.

Fig. 3.
Fig. 3.

RF spectrum analyzer measurement under zero optical path length difference in the two paths.

Fig. 4.
Fig. 4.

Signal frequency spectrum under different fiber delays (a) balanced interferometer, zero path length difference; (b) small path length difference, e.g., 1.1 m; (c) moderate path length difference, e.g., 4.2 m; and (d) long path length difference, e.g., 9.5 m.

Fig. 5.
Fig. 5.

Using the tunable delay to compensate the unequal path length.

Fig. 6.
Fig. 6.

Comparison of the frequency spectrum of the beat signal (a) with and (b) without compensation.

Fig. 7.
Fig. 7.

All-fiber based LDV acoustic detection system using an inexpensive short coherence length laser and tunable optical delay.

Fig. 8.
Fig. 8.

RF spectrum analyzer traces showing the frequency spectrum of the detected signal for an LDV system using a short coherence length laser (a) without and (b) with the fiber delay compensation technique.

Fig. 9.
Fig. 9.

The obtained signal frequency spectrum by using (a) long coherence length laser and (b) short coherence length laser.

Fig. 10.
Fig. 10.

Proposed ODL for actively adjusting the range of the all-fiber LDV to the desired operational distance. The ODL consists of one switched digital ODL and one continuous ODL.

Fig. 11.
Fig. 11.

Equivalent delay path length obtained by the combination of the 128 (1 to 127) different delay settings of the switched digital ODL (diamonds) and the continuous ODL (squares).

Fig. 12.
Fig. 12.

Simulation results for the noise induced for the detected signal by the optical delay line resolution and equivalently the optical path length difference of 0.1 m between the two interferometer arms.

Equations (6)

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Etrans=A1ej2π(f0Δf)t+A2ej2πf0t+A3ej2π(f0+Δf)t,
ELO=A1ej2π(f0+fmΔf)t+A2ej2π(f0+fm)t+A3ej2π(f0+fm+Δf)t,
I=(Etrans+ELO)(Etrans+ELO)*,
Iobse=|A|2[6cos(2πfmt)+4cos(2π(fm+Δf)t)+4cos(2π(fmΔf)t)+2cos(2π(fm+2Δf)t)+2cos(2π(fm2Δf)t)].
S(ω,τ)=12P0τc1+(ω±Ω)2{1eτ/τc[cos(ω±Ω)τ+sin(ω±Ω)τ(ω±Ω)τc]}+12P02πeτ/τcδ(ω±Ω),
T=(b020+b121++bN2N)τ,

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