Optical fiber Fabry-Perot sensors for smart structures

Lee, C E; Alcoz, J.J.; Yeh, Yun-Hae; Gibler, William N.; Atkins, Robert; Taylor, Henry F.

doi:10.1088/0964-1726/1/2/004

Cited by 33 publications

(21 citation statements)

References 12 publications

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“…These losses may be addressed technically, by use of additional reference power measurements, for example, but an alternative to intensity measurement is desirable. Interferometry offers a potential alternative, in which the sensing element is a length of fiber between a pair of partially reflecting splices 5 or a pair of matched Bragg gratings. 6 To produce these designs, single-mode fiber rather than conventional multimode POF is required.…”

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Strain and temperature sensitivity of a single-mode polymer optical fiber

et al. 2005

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We have measured the optical phase sensitivity of fiber based on poly(methyl methacrylate) under nearsingle-mode conditions at 632.8 nm wavelength. The elongation sensitivity is 131± 3 ϫ 10 5 rad m −1 and the temperature sensitivity is −212± 26 rad m −1 K −1 . These values are somewhat larger than those for silica fiber and are consistent with the values expected on the basis of the bulk polymer properties. © 2005 Optical Society of America OCIS codes: 060.2300, 060.2370 Fiber optic strain sensors offer advantages that include insensitivity to electromagnetic fields, light weight, and minimal intrusiveness 1 compared with conventional strain gauges. Fused silica, the material of choice for the majority of optical fibers, has near-ideal mechanical characteristics for many strain-sensing applications. However, fused-silica fibers have an upper strain limit of approximately 3-5% and in general are reliable only to ϳ1% strain after selection of fibers by proof testing.2 In highly loaded engineering structures such as highway bridges, buildings, and aircraft wings, transverse loading can result in large bending strains, which can induce locally high strains, so monitoring structural strain is becoming increasingly important. With the advent of new engineering materials, such as composites, the acceptable range of applied strain can exceed the breaking strain of fused-silica fiber, precluding the use of standard fiber-based strain gauges. The inherent fracture toughness and flexibility of polymer optical fibers (POFs) makes them much more suitable in high-strain applications than their glass-based counterparts. In addition, fiber Bragg gratings have recently been written into POFs, broadening their potential applications. 3POF sensors for strain and curvature measurement have been reported in the literature. 4 However, these measurements have generally been intensiometric measurements made with multimode fibers. Whereas robust sensors have been demonstrated to use intensity modulating mechanisms, they are susceptible to unwanted intensity losses, for example, bend loss or connector loss, and to variations in source power. These losses may be addressed technically, by use of additional reference power measurements, for example, but an alternative to intensity measurement is desirable. Interferometry offers a potential alternative, in which the sensing element is a length of fiber between a pair of partially reflecting splices 5 or a pair of matched Bragg gratings. 6 To produce these designs, single-mode fiber rather than conventional multimode POF is required. The advent of single-mode POF offers the potential for highstrain fiber sensors to exploit the advantages of interferometry. We report here interferometric measurement of the optical phase sensitivities of single-mode POF versus strain and temperature changes.The POF (Paradigm Optics) used in these experiments had a cladding diameter of ϳ125 m (commercial acrylic with n = 1.4905) and a core diameter of 6 m [poly(methyl methacrylate) (PMMA) doped with Ͻ3% polysty...

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Strain and temperature sensitivity of a single-mode polymer optical fiber

et al. 2005

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“…For intrinsic sensors, previous work by Lee et al 16 has shown that the addition of coatings to produce stronger reflections from the fibre ends has resulted in lower strength fusion splices when compared to those produced using clean fibre-to-fibre splices 17 . …”

Section: Specific Problems With Fp-based Sensor Constructionmentioning

confidence: 99%

Low cost optical fibre based Fabry–Perot strain sensor production

Tuck

Hague

Doyle³

2006

Meas. Sci. Technol.

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The production of Fabry–Perot-based optical fibre sensors has long been an iterative and labour-intensive process. This paper demonstrates the production of Fabry–Perot-based optical fibre strain sensors using chemical etching techniques. Utilizing hydrofluoric acid and single-mode optical fibres, a preferential etching mechanism was observed around the core portion of the fibres. These etched fibre ends were then spliced together successfully to form enclosed Fabry–Perot cavities between 18 and 60 µm in length. These sensors have then been deployed for strain monitoring and have been subjected to strains of up to 1400 με on tensile test specimens. Etched Fabry–Perot cavity lengths were monitored using a white light interferometry system based on a CCD spectrometer and an 850 nm super luminescent diode. A linear and repeatable response to these strain tests has been shown with negligible sensitivity to temperature.

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“…where R 1 and R 2 are the reflectance of the reflectors and A is the cavity losses [20]. The strain on the EFPI due to mechanical perturbation is given by:…”

Section: Efpi Sensor and Sinusoidal Strainmentioning

confidence: 99%

Modal analysis using the Bessel harmonics of an extrinsic Fabry-Perot interferometric sensor (EFPI) and neural networks

Abdi

Watkins

2006

SPIE Proceedings

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A demodulation system employing neural networks is used to process the non-linear signal from an extrinsic FabryPerot interferometric (EFPI) sensor. A sinusoidal strain is theoretically shown to produce well-defined Bessel harmonics in the EFPI signal. The neural network demodulator (NND) uses a Fourier Series Neural Network to separate the Bessel harmonic components of the EFPI signal and a Back-Propagation Neural Network is used to predict the strain levels through the analysis of the Bessel harmonics. The NND is first simulated in a computer program and then actually employed in an experimental setting to determine the frequency response of a 25 cm composite cantilever beam. A function generator was used to drive a PZT actuator attached to the composite beam and the resulting periodic strain was measured by the EFPI; the frequency of the composite beam was varied between 10 Hz and 900 Hz. The NND demodulated the EFPI signal and determined the frequency response of the composite beam. The results show that the NND accurately reproduced the natural frequencies and mode shapes of the cantilever beam.

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Optical fiber Fabry-Perot sensors for smart structures

Cited by 33 publications

References 12 publications

Strain and temperature sensitivity of a single-mode polymer optical fiber

Strain and temperature sensitivity of a single-mode polymer optical fiber

Low cost optical fibre based Fabry–Perot strain sensor production

Modal analysis using the Bessel harmonics of an extrinsic Fabry-Perot interferometric sensor (EFPI) and neural networks

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