Abstract

We demonstrate and analyze a novel fiber optic confocal laser Doppler velocimeter using an ultra-narrow linewidth all-fiber laser source centered at around 1550 nm (eye-safe region). The narrow spectral linewidth of the fiber laser (<10 kHz) is used to achieve an extremely high velocity resolution (~0.0075 m/s), which is an order of magnitude better as compared to the commonly used semiconductor diode lasers or He-Ne lasers based systems. The directional optical circulator based design used in our system is much simpler to implement and is power conserving compared to the conventional Michelson interferometer based designs. We perform Gaussian beam propagation analysis by using the ABCD law to study the performance of the confocal design. The analysis is in good accord with our experimental results. The confocal design is capable of providing ultrahigh spatial resolution (~5μm, in both lateral and longitudinal directions) for high-precision velocity distribution measurement applications.

© 2005 Optical Society of America

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References

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  1. Y. Yeh, and H. Z. Cumming, �??Localized fluid flow measurement with a He-Ne laser spectrometer,�?? Appl. Phys. Lett. 4, 176-178, 1964.
    [CrossRef]
  2. T. Tanaka, C. Riva, and I Ben-Sira, �??Blood velocity measurements in human retinal vessels,�?? Science 186, 830-831, 1974.
    [CrossRef] [PubMed]
  3. H. Nishihara, J. Koyama, N. Hoki, F. Kajiya, M. Hironaga, and M. Kano, �??Optical-fiber laser Doppler velocimeter for high-resolution measurement of pulsatile blood flows,�?? Appl. Opt. 21, 1785-1790, 1982.
    [CrossRef] [PubMed]
  4. A. P. Shepherd, and P. �?. �?berg, ed., Laser Doppler blood flowmetry, (Kluwer Academic Publishers, Norwell, Massachusttes, 1990).
  5. H. Nishihara, K. Matsumoto, and J. Koyama, �??Use of a laser diode and an optical fiber for a compact laser-Doppler velocimeter,�?? Opt. Lett. 9, 62-64, 1984.
    [CrossRef] [PubMed]
  6. M. D. Stern, and D. L. Lappe, �??Method and apparatus for measurement of blood flow using coherent light,�?? U. S. Patent 4,109,647 (1978).
  7. K. Kyuma, S. Tai, K. Hamanaka, and M. Nunoshita, �??Laser Doppler velocimeter with a novel optical fiber probe,�?? Appl. Opt. 20, 2424-2427, 1981.
    [CrossRef]
  8. V. Gusmeroli, and M. Martinelli, �??Ditributed laser Doppler velocimeter,�?? Opt. Lett. 16, 1358-1360, 1991.
    [CrossRef] [PubMed]
  9. E. T. Shimizu, �??Directional discrimination in the self-mixing type laser Doppler velocimeter,�?? Appl. Opt. 26, 4541-4544, 1987.
    [CrossRef] [PubMed]
  10. Y. W. Song, S. A. Havstad, D. Starodubov, Y. Xie, A. A. Willner, and J. Feinberg, �??40-nm-wide tunable fiber ring laser with single-mode operation using a highly stretchable FBG,�?? IEEE Photonics Technol. Lett. 13, 1167-1169 (2001).
    [CrossRef]
  11. U. Sharma, C. S. Kim, and J. U. Kang, �??Highly stable tunable dual-wavelength Q-switched fiber laser for DIAL application,�?? IEEE Photonics Technol. Lett. 16, 1277-1279, 2004.
    [CrossRef]
  12. S. W. James, R. A. Lockey, D. Egan, and R. P. Tatam, �??Fiber optic based reference beam laser Doppler velocimetry,�?? Opt. Commun. 119, 460-464, 1995.
    [CrossRef]
  13. G. P. Agrawal, Nonlinear fiber optics, Chapter 2, (Academic Press Inc., San Diego, 1995).

Appl. Opt.

Appl. Phys. Lett.

Y. Yeh, and H. Z. Cumming, �??Localized fluid flow measurement with a He-Ne laser spectrometer,�?? Appl. Phys. Lett. 4, 176-178, 1964.
[CrossRef]

IEEE Photonics Technol. Lett.

Y. W. Song, S. A. Havstad, D. Starodubov, Y. Xie, A. A. Willner, and J. Feinberg, �??40-nm-wide tunable fiber ring laser with single-mode operation using a highly stretchable FBG,�?? IEEE Photonics Technol. Lett. 13, 1167-1169 (2001).
[CrossRef]

U. Sharma, C. S. Kim, and J. U. Kang, �??Highly stable tunable dual-wavelength Q-switched fiber laser for DIAL application,�?? IEEE Photonics Technol. Lett. 16, 1277-1279, 2004.
[CrossRef]

Opt. Commun.

S. W. James, R. A. Lockey, D. Egan, and R. P. Tatam, �??Fiber optic based reference beam laser Doppler velocimetry,�?? Opt. Commun. 119, 460-464, 1995.
[CrossRef]

Opt. Lett.

Science

T. Tanaka, C. Riva, and I Ben-Sira, �??Blood velocity measurements in human retinal vessels,�?? Science 186, 830-831, 1974.
[CrossRef] [PubMed]

Other

A. P. Shepherd, and P. �?. �?berg, ed., Laser Doppler blood flowmetry, (Kluwer Academic Publishers, Norwell, Massachusttes, 1990).

M. D. Stern, and D. L. Lappe, �??Method and apparatus for measurement of blood flow using coherent light,�?? U. S. Patent 4,109,647 (1978).

G. P. Agrawal, Nonlinear fiber optics, Chapter 2, (Academic Press Inc., San Diego, 1995).

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Figures (5)

Fig. 1.
Fig. 1.

Schematic configuration of the fiber optic confocal Doppler flowmeter using a narrow linewidth all-fiber laser source.

Fig. 2.
Fig. 2.

Experimental (solid) and simulation (dashed) results of longitudinal resolution (FWHM) of the fiber optic confocal setup for various combinations of microscopic objective lenses. The measured FWHM was found to be (a) 5X: 102 μm, (b) 10X: 28.4 μm , (c) 20X: 11 μm, and (d) 40X: 4.4 μm, respectively

Fig. 3.
Fig. 3.

Doppler shifted frequency measurements of the transducer membrane vibrations at 1 kHz for different levels of applied RF voltage. a) photodetector spectrum in absence of transducer membrane motion. The maximum velocity and the maximum displacement were calculated to be, b) 0.126 m/s, 31 μm, c) 0.215 m/s, 53 μm, and d) 0.35 m/s, 87 μm, respectively.

Fig. 4.
Fig. 4.

Doppler frequency spectra of the measured and simulation (thick lines) results. a). 5X objective lens: Doppler shifted frequencies corresponding to the whole range of the transducer membrane motion with almost uniform amplitude are observed. b). 40X objective lens: Doppler shifted frequencies from a highly localized region (<5μm) can be extracted, thereby providing a high longitudinal resolution.

Fig. 5.
Fig. 5.

Theoretical (solid line) and experimental (points with error bars) velocity distribution of the elctroacoustic transducer membrane as a function of displacement from its mean position. The error bars corresponds to the longitudinal resolution of the confocal Doppler velocimeter.

Equations (17)

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Δν x y z = 2 cos ( θ 2 ) λ V x y z cos ( ϕ )
Δν x y x = 2 λ V x y z
q 2 = Aq 1 + B Cq 1 + D
A = D = f 2 2 2 L 1 f 2 + 2 f 1 f 2 2 L 2 f 2 + 2 L 2 L 1 2 L 2 f 1 f 2 2
B = f 1 2 f 2 2 ( f 2 L 2 )
C = 2 ( f 1 + f 2 L 1 ) ( f 1 f 2 L 1 L 2 + L 2 L 1 L 2 f 1 L 2 f 2 ) f 1 2 f 2 2
A = D = 1 , C = 0 , B = 2 f 1 2 f 2 2 ( f 2 L 2 )
1 q 1 = 1 R 1 i λ πw 0 2 = i λ πw 0 2
q 2 = q 1 2 f 1 2 f 2 2 ( f 2 L 2 ) = i πw 0 2 λ 2 f 1 2 f 2 2 ( f 2 L 2 )
1 q 2 = 1 R 2 i λ π w 2 2
R 2 = ( πw 0 2 λ ) 2 + 4 ( f 1 f 2 ) 4 ( f 2 L 2 ) 2 2 f 1 2 f 2 2 ( f 2 L 2 )
w 2 2 = ( λ πw 0 ) 2 [ ( π w 0 2 λ ) 2 + 4 ( f 1 f 2 ) 4 ( f 2 L 2 ) 2 ]
P 2 = s R s P 0 w 2 2 exp ( x 2 + y 2 w 2 2 ) dxdy = π R s P 0 [ 1 exp ( ( r 0 w 2 ) 2 ) ]
PCR = [ 1 exp ( ( r 0 w 2 ) 2 ) ] [ 1 exp ( ( r 0 w 0 ) 2 ) ] = [ 1 exp ( ( r 0 w 2 ) 2 ) ] [ 1 1 e ]
V ( L 2 ) = V Max cos ( π Δ d ( L 2 f 2 ) )
w 2 ( Δ v ) 2 = ( λ πw 0 ) 2 [ ( πw 0 2 λ ) 2 + 4 ( f 1 f 2 ) 4 ( Δ d π cos 1 ( ( Δ v Δ v max ) ) 2 ]
PCR ( Δ v ) = [ 1 exp ( ( r 0 w 2 ( Δ v ) ) 2 ) ] [ 1 1 e ]

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