Abstract

A two-loop Sagnac interferometer is proposed for fiber-optic distributed sensing. The location of a disturbance can be determined from the two output phase signals of the two Sagnac loops, and the amplitude of the disturbance can be obtained by integration of the phase signal. A prototype distributed impact sensing system has been tested based on the two-loop Sagnac interferometer.

© 1996 Optical Society of America

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References

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  1. A. J. Rogers, Appl. Opt. 20, 1060 (1981).
    [CrossRef] [PubMed]
  2. J. P. Dakin, Proc. SPIE 1797, 76 (1992).
    [CrossRef]
  3. A. D. Kersey, Proc. SPIE 1797, 161 (1992).
    [CrossRef]
  4. P. L. Fuhr, W. B. Spillman, B. R. Kline, J. R. Lord, Opt. Eng. 29, 148 (YEAR).
  5. J. L. Brooks, J. Lightwave Technol. 1, 1062 (1983).
  6. V. Gusmeroli, J. Lightwave Technol. 11, 1681 (1993).
    [CrossRef]
  7. J. P. Dakin, D. A. Pearce, A. P. Strong, C. A. Wade, Proc. SPIE 838, 325 (1987).
  8. E. Udd, “Sagnac distributed sensor,”U.S. patent4,976,507 (December11, 1990).
  9. A. D. Kersey, A. C. Lewin, D. A. Jackson, Electron. Lett. 20, 368 (1984).
    [CrossRef]

1993

V. Gusmeroli, J. Lightwave Technol. 11, 1681 (1993).
[CrossRef]

1992

J. P. Dakin, Proc. SPIE 1797, 76 (1992).
[CrossRef]

A. D. Kersey, Proc. SPIE 1797, 161 (1992).
[CrossRef]

1987

J. P. Dakin, D. A. Pearce, A. P. Strong, C. A. Wade, Proc. SPIE 838, 325 (1987).

1984

A. D. Kersey, A. C. Lewin, D. A. Jackson, Electron. Lett. 20, 368 (1984).
[CrossRef]

1983

J. L. Brooks, J. Lightwave Technol. 1, 1062 (1983).

1981

Brooks, J. L.

J. L. Brooks, J. Lightwave Technol. 1, 1062 (1983).

Dakin, J. P.

J. P. Dakin, Proc. SPIE 1797, 76 (1992).
[CrossRef]

J. P. Dakin, D. A. Pearce, A. P. Strong, C. A. Wade, Proc. SPIE 838, 325 (1987).

Fuhr, P. L.

P. L. Fuhr, W. B. Spillman, B. R. Kline, J. R. Lord, Opt. Eng. 29, 148 (YEAR).

Gusmeroli, V.

V. Gusmeroli, J. Lightwave Technol. 11, 1681 (1993).
[CrossRef]

Jackson, D. A.

A. D. Kersey, A. C. Lewin, D. A. Jackson, Electron. Lett. 20, 368 (1984).
[CrossRef]

Kersey, A. D.

A. D. Kersey, Proc. SPIE 1797, 161 (1992).
[CrossRef]

A. D. Kersey, A. C. Lewin, D. A. Jackson, Electron. Lett. 20, 368 (1984).
[CrossRef]

Kline, B. R.

P. L. Fuhr, W. B. Spillman, B. R. Kline, J. R. Lord, Opt. Eng. 29, 148 (YEAR).

Lewin, A. C.

A. D. Kersey, A. C. Lewin, D. A. Jackson, Electron. Lett. 20, 368 (1984).
[CrossRef]

Lord, J. R.

P. L. Fuhr, W. B. Spillman, B. R. Kline, J. R. Lord, Opt. Eng. 29, 148 (YEAR).

Pearce, D. A.

J. P. Dakin, D. A. Pearce, A. P. Strong, C. A. Wade, Proc. SPIE 838, 325 (1987).

Rogers, A. J.

Spillman, W. B.

P. L. Fuhr, W. B. Spillman, B. R. Kline, J. R. Lord, Opt. Eng. 29, 148 (YEAR).

Strong, A. P.

J. P. Dakin, D. A. Pearce, A. P. Strong, C. A. Wade, Proc. SPIE 838, 325 (1987).

Udd, E.

E. Udd, “Sagnac distributed sensor,”U.S. patent4,976,507 (December11, 1990).

Wade, C. A.

J. P. Dakin, D. A. Pearce, A. P. Strong, C. A. Wade, Proc. SPIE 838, 325 (1987).

Appl. Opt.

Electron. Lett.

A. D. Kersey, A. C. Lewin, D. A. Jackson, Electron. Lett. 20, 368 (1984).
[CrossRef]

J. Lightwave Technol.

J. L. Brooks, J. Lightwave Technol. 1, 1062 (1983).

V. Gusmeroli, J. Lightwave Technol. 11, 1681 (1993).
[CrossRef]

Opt. Eng.

P. L. Fuhr, W. B. Spillman, B. R. Kline, J. R. Lord, Opt. Eng. 29, 148 (YEAR).

Proc. SPIE

J. P. Dakin, Proc. SPIE 1797, 76 (1992).
[CrossRef]

A. D. Kersey, Proc. SPIE 1797, 161 (1992).
[CrossRef]

J. P. Dakin, D. A. Pearce, A. P. Strong, C. A. Wade, Proc. SPIE 838, 325 (1987).

Other

E. Udd, “Sagnac distributed sensor,”U.S. patent4,976,507 (December11, 1990).

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Figures (4)

Fig. 1
Fig. 1

Structure of a two-loop Sagnac interferometer for distributed sensing. LED, light-emitting diode; PD’s, phase detectors; BPF’s, bandpass filters.

Fig. 2
Fig. 2

Equivalent representation of the two embedded Sagnac loops in Fig. 1 for (a) the shorter loop and (b) the longer loop.

Fig. 3
Fig. 3

Output phase signals from the two Sagnac loops (solid traces) and their ratio (dotted–dashed trace).

Fig. 4
Fig. 4

Comparison of the phase ratio R(x) obtained from the experiment (open circles) and from theory (solid curve).

Equations (9)

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E CW , a = E a cos [ ω t - φ ( t - x / v ) ] ,
E CCW , a = E a cos [ ω t - φ ( t - ( L S - x ) / v ) ] ,
Δ φ a = φ ( t - x / v ) - φ [ t - ( L S - x ) / v ] L S - 2 x v d φ d t .
I a = L 0 cos 2 [ k a sin ( ω 1 t ) + Δ φ a ] ,
k a = k L S ω 1 v ,
Δ φ b = φ ( t - x / v ) - φ [ t - ( L S + 2 L D - x ) / v ] L S + 2 L D - 2 x v d φ d t 2 L S - 2 x v d φ d t             ( for  L S = 2 L D ) .
I b = I 0 cos 2 [ k b sin ( ω 2 t ) + Δ φ b ] ,
R ( x ) = Δ φ a Δ φ b = L S - 2 x 2 L S - 2 x .
x = 1 - 2 R ( x ) 2 - 2 R ( x ) L S             ( for  L S = 2 L D ) .

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