Abstract

A fiber-optic extrinsic Fabry-Perot interferometer strain sensor (EFPI-S) of ls=2.5 cm sensor length using three-wavelength digital phase demodulation is demonstrated to exhibit <50 pm displacement resolution (< 2nm/m strain resolution) when measuring the cross expansion of a PZT-ceramic plate. The sensing (single-mode downlead-) and reflecting fibers are fused into a 150/360 µm capillary fiber where the fusion points define the sensor length. Readout is performed using an improved version of the previously described three-wavelength digital phase demodulation method employing an arctan-phase stepping algorithm. In the present experiments the strain sensitivity was varied via the mapping of the arctan - lookup table to the 16-Bit DA-converter range from 188.25 µε/V (6 Volt range 1130 µε) to 11.7 µε/Volt (range 70 µε).

© Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |

  1. M. Schmidt, N. F�rstenau, "Fiber-optic extrinsic Fabry-Perot interferometer sensors with three-wavelength digital phase demodulation," Opt. Lett. 24, 599 - 601 (1999)
    [CrossRef]
  2. T.Melz, M. Fr�vel, V.Krajenski, M.A. de la Torre, H. Hanselka, J. M. Pintado, "Modelling and control of adaptive mechanical structures", in: Gabbert, Ulrich (Eds.): Fortschritt-Berichte VDI : ser. no. 11, Schwin-gungstechnik 268, 449 - 458 (1998)
  3. K.A.Murphy, M.A. Gunther, A. M. Vengsarkar, R.O. Claus, "Quadrature phase shifted extrinsic Fabry-Perot optical fiber sensors," Opt. Lett. 16, 273-275 (1991)
    [CrossRef] [PubMed]
  4. V. Bhatia, K.A. Murphy, R.O. Claus, M. E. Jones, J. L. Grace, T.A. Tran, J.A. Greene, "Multiple strain state measurements using conventional and absolute optical fiber-based extrinsic Fabry-Perot interferometric strain sensors," Smart Materials Struct. 4, 240 -245 (1995)
    [CrossRef]
  5. T. Li, R.G.May, A. Wang, R.O. Claus, "Optical scanning extrinsic Fabry-Perot interferometer for absolute microdisplacement measurement," Appl. Opt. 36, 8858 � 8861 (1997)
    [CrossRef]
  6. M. Schmidt, N. F�rstenau, W. Bock, W. Urbanczyk, "Fiber-optic polarimetric strain sensor with three-wavelength digital phase demodulation," Opt. Lett. 25 1334-1336 (2000)
    [CrossRef]

Other (6)

M. Schmidt, N. F�rstenau, "Fiber-optic extrinsic Fabry-Perot interferometer sensors with three-wavelength digital phase demodulation," Opt. Lett. 24, 599 - 601 (1999)
[CrossRef]

T.Melz, M. Fr�vel, V.Krajenski, M.A. de la Torre, H. Hanselka, J. M. Pintado, "Modelling and control of adaptive mechanical structures", in: Gabbert, Ulrich (Eds.): Fortschritt-Berichte VDI : ser. no. 11, Schwin-gungstechnik 268, 449 - 458 (1998)

K.A.Murphy, M.A. Gunther, A. M. Vengsarkar, R.O. Claus, "Quadrature phase shifted extrinsic Fabry-Perot optical fiber sensors," Opt. Lett. 16, 273-275 (1991)
[CrossRef] [PubMed]

V. Bhatia, K.A. Murphy, R.O. Claus, M. E. Jones, J. L. Grace, T.A. Tran, J.A. Greene, "Multiple strain state measurements using conventional and absolute optical fiber-based extrinsic Fabry-Perot interferometric strain sensors," Smart Materials Struct. 4, 240 -245 (1995)
[CrossRef]

T. Li, R.G.May, A. Wang, R.O. Claus, "Optical scanning extrinsic Fabry-Perot interferometer for absolute microdisplacement measurement," Appl. Opt. 36, 8858 � 8861 (1997)
[CrossRef]

M. Schmidt, N. F�rstenau, W. Bock, W. Urbanczyk, "Fiber-optic polarimetric strain sensor with three-wavelength digital phase demodulation," Opt. Lett. 25 1334-1336 (2000)
[CrossRef]

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (4)

Fig 1:
Fig 1:

Schematic of three - wavelength EFPI sensor system. SLD/ELED=light source, “2”=temperature sensor, “3”=temperature control, 2×2 and 3×1=directional couplers, Θ1,2,3=angles between interference filter normal and collimating grin lenses. Inset shows details of EFPI-S sensing element.

Figure 2:
Figure 2:

Two Extrinsic Fabry - Perot Interferometer strain sensors (sensing length l=24.5 mm and 50.7 mm) surface adhered to a piezo-electric (PZT) actuator (thickness 1 mm).

Figure 3:
Figure 3:

3-λ output signals with 1800 V PZT excitation at 10 Hz. Lower traces: interference signals; upper trace: phase demodulated signal ~ L(t) after DA-conversion.

Figure 4:
Figure 4:

High resolution strain measurement with PZT excitation Upp=40 mVolt at 40 Hz (Ch3). Demodulated signal amplitude (Ch4, upper trace) corresponds to strain amplitude (peak-peak) ε=4.5 nm/m.

Equations (4)

Equations on this page are rendered with MathJax. Learn more.

U i ( t ) = U 0 ( R 1 + R 2 eff ) ( 1 μ i ( Φ i ) cos { Φ i ( t ) + Δ Φ 2 i } )
μ ( Φ ) = 2 R 1 R 2 eff R 1 + R 2 eff exp { Φ ( t ) 2 ( δλ 4 ln 2 λ ) 2 } .
Φ = arc tan [ U 1 U 3 U 1 + U 3 2 U 2 f ( δ Δ Φ ij ) ] ± m π
S Φ = ε Δ Φ = λ 4 πl S

Metrics