Determination of the individual strain-optic coefficients in single-mode optical fibres

Bertholds, A.; Dändliker, R.

doi:10.1109/50.3956

Cited by 254 publications

(106 citation statements)

References 14 publications

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“…For the PMMA the Pockels coefficients are 8 p 11 = 0.300 and p 12 = 0.297 and the Poisson ratio is 9 = 0.34, which gives a value d⌽ /dL = 132.6 ϫ 10 5 rad m −1 , in good agreement with the experimental result. Table 1 lists the phase response d⌽ /dL of standard silica fiber, 10,11 that of the polymer fiber studied in this Letter, and the values predicted from theory using the coefficients for bulk PMMA. 12,13 The measured strain sensitivity of polymer fiber is ϳ14% larger than that for silica fiber.…”

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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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“…The common attenuation α of fibres [5] as well as their refractive indices n for various wavelengths [6][7][8] are depicted in Table 1. The Pockels coefficients of fused silica are P 11 =0.113 and P 12 =0.252 [9] and the Poisson's ratio is μ=0.17 [10]. For poly(methyl methacrylate) (PMMA) fibre these values are P 11 =0.300 and P 12 =0.297 [11] and μ=0.34 [12].…”

Section: Optimum Cavity Length For Maximum Strain Sensitivitymentioning

confidence: 92%

Optimisation of polymer optical fibre based interferometric sensors

Pospori

Webb

2015

Micro-Structured and Specialty Optical Fibres IV

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A numerical model for studying the performance of polymer optical fibre-based interferometric sensors is presented. The strain sensitivity of Fabry-Perot and two-beam interferometric sensors is investigated by varying the physical and optical properties corresponding to frequently used wavelengths. The developed model was used to identify the regimes in which these devices offer enhanced performance over their silica counterparts when used for stress sensing.

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“…The typical Pockel's coefficients 22,23 , Poisson ratio 21,24 , attenuation 25 and refractive indices 26,27 for λ=850 nm and λ=1550 nm of PMMA and silica optical fibres are shown in table 1. …”

Section: Fabry-perot Interferometermentioning

confidence: 99%

Performance analysis of polymer optical fibre based Fabry-Perot sensor formed by two uniform Bragg gratings

Pospori

Webb

2016

SPIE Proceedings

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The stress sensitivity of polymer optical fibre (POF) based Fabry-Perot sensors formed by two uniform Bragg gratings with finite dimensions is investigated. POF has received high interest in recent years due to its different material properties compared to its silica counterpart. Biocompatibility, a higher failure strain and the highly elastic nature of POF are some of the main advantages. The much lower Young's modulus of polymer materials compared to silica offers enhanced stress sensitivity to POF based sensors which renders them great candidates for acoustic wave receivers and any kind of force detection. The main drawback in POF technology is perhaps the high fibre loss. In a lossless fibre the sensitivity of an interferometer is proportional to its cavity length. However, the presence of the attenuation along the optical path can significantly reduce the finesse of the Fabry-Perot interferometer and it can negatively affect its sensitivity at some point. The reflectivity of the two gratings used to form the interferometer can be also reduced as the fibre loss increases. In this work, a numerical model is developed to study the performance of POF based Fabry-Perot sensors formed by two uniform Bragg gratings with finite dimensions. Various optical and physical properties are considered such as grating physical length, grating effective length which indicates the point where the light is effectively reflected, refractive index modulation of the grating, cavity length of the interferometer, attenuation and operating wavelength. Using this model, we are able to identify the regimes in which the PMMA based sensor offer enhanced stress sensitivity compared to silica based one.

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Determination of the individual strain-optic coefficients in single-mode optical fibres

Cited by 254 publications

References 14 publications

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

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

Optimisation of polymer optical fibre based interferometric sensors

Performance analysis of polymer optical fibre based Fabry-Perot sensor formed by two uniform Bragg gratings

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