Mode coupling in large-diameter polymer-clad silica fibers

Ruddy, Vincent P.; Shaw, Gerard

doi:10.1364/ao.34.001003

Cited by 25 publications

(8 citation statements)

References 6 publications

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“…Analysis of data on mode coupling from a variety of step-index multimode optical fibers (Table ) reveals that mode coupling is a strong function of fiber attenuation. ,,, This attenuation- dependent mode coupling leads to the rapid development of a steady-state distribution of modes. Another source of mode coupling arises from inhomogeneities in the refractive index of the fiber cladding at the core/cladding interface.…”

Section: Resultsmentioning

confidence: 99%

“…Knowledge of the MPD in the sensing zone is essential for quantitative evanescent-wave detection and for effective design of a wide range of sensors, including those based on refractive index, absorbance, or fluorescence detection. Mode coupling, which is due primarily to scattering and absorption within the fiber core and at the core−cladding interface, results in a loss of some higher-order core modes into the cladding and a concentration of lower-order (on-axis) modes that increases with distance from the source . As a result, mode coupling in a multimode evanescent-wave sensor alters the sensitivity of the sensor and increases the analyte-independent optical loss.…”

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confidence: 99%

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Use of Analyte-Modulated Modal Power Distribution in Multimode Optical Fibers for Simultaneous Single-Wavelength Evanescent-Wave Refractometry and Spectrometry

1999

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A new method is described for the simultaneous determination of absorbance and refractive index of a sample medium. The method is based on measurement of the analyte-modulated modal power distribution (MPD) in a multimode waveguide. In turn, the MPD is quantified by the far-field spatial pattern and intensity of light, i.e., the Fraunhofer diffraction pattern (registered on a CCD camera), that emerges from a multimode optical fiber. Operationally, light that is sent down the fiber interacts with the surrounding analyte-containing medium by means of the evanescent wave at the fiber boundary. The light flux in the propagating beam and the internal reflection angles within the fiber are both affected by optical absorption connected with the analyte and by the refractive index of the analyte-containing medium. In turn, these angles are reflected in the angular divergence of the beam as it leaves the fiber. As a result, the Fraunhofer diffraction pattern of that beam yields two parameters that can, together, be used to deduce refractive index and absorbance. This MPD based detection offers important advantages over traditional evanescent-wave detection strategies which rely on recording only the total transmitted optical power or its lost fraction. First, simultaneous determination of sample refractive index and absorbance is possible at a single probe wavelength. Second, the sensitivity of refractometric and absorption measurements can be controlled simply, either by adjusting the distance between the end face of the fiber and the CCD detector or by monitoring selected modal groups at the fiber output. As a demonstration of these capabilities, several weakly absorbing solutions were examined, with refractive indices in the range from 1.3330 to 1.4553 and with absorption coefficients in the range 0-16 cm-1. The new detection strategy is likely to be important in applications in which sample coloration varies and when it is necessary to compensate for variations in the refractive index of a sample.

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Use of Analyte-Modulated Modal Power Distribution in Multimode Optical Fibers for Simultaneous Single-Wavelength Evanescent-Wave Refractometry and Spectrometry

1999

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“…Thus, for a given L, η j directly defines the sensitivity [13]. Owing to the high-order modes being excited repeatedly at the first transition of each segmented region, the SS EW sensor can effectively stimulate the fiber low-order modes to the high-order modes [21]. When ξ (the number of segments) increases, the stimulation from the loworder modes to the high-order modes will be more effective.…”

Section: Theorymentioning

confidence: 99%

Fiber-optic evanescent wave sensor with a segmented structure

Liu

et al. 2014

Appl. Opt.

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A segmented structure optic fiber sensor is proposed and demonstrated; it is based on evanescent wave absorption theory. The waveguide modes of the segmented structure are simulated and analyzed by using the beam propagation method, which shows the high-order modes are excited repeatedly at the first transition of each segmented region. The effect of the number of segments and the core diameters on the sensitivity of the sensors is investigated experimentally. The sensitivity of the sensors is tested by using different concentrations of methylene blue solution. The experimental results show that our sensor's sensitivity is ∼0.0476 L/g, which is two times higher than that of the conventional single straight sensor, with the same core diameters and length of the sensing region, and the absorbance is linearly proportional to the number of segments, while being inversely proportional to the residue core diameter of the etched segments within the concentration range from 2 to 14 g/L. These results are consistent with theoretical models and simulation analysis. The proposed sensor not only has high sensitivity, but it is also robust due to the large core diameter of the segmented region, which is suitable for materials spectrum measurements.

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“…The absorbable power ratio is derived by ¼ p a / p t , and p t is the total pump power. Some experiments have demonstrated that the mode coupling coefficient is not a constant, but is proportional to 1/z 1/2 [7], so in the following calculation we chose ¼ 0 /z 1/2 instead of a constant . The total absorption efficiency versus the fiber length by both calculation and fitting is given in Figure 5.…”

Section: Theorymentioning

confidence: 99%

Efficiency of pump absorption in gain-guided and index-antiguided (GG-IAG) fiber

Yan

Zhou

Wei

et al. 2010

Journal of Modern Optics

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In this paper, the absorption characteristics of a novel double-clad gain-guided and index-antiguided (GG-IAG) fiber are investigated with 3D ray-trace method. Additionally, the simulated correctness compared with real data was carried out by measuring the GG-IAG fiber. Analysis and experimental results show that the absorption characteristics of GG-IAG fibers are different from conventional fibers: the total absorption efficiency of a GG-IAG fiber is large, while the effective absorption length is very short, and the negative refractive index step has significant influence on the total absorption efficiency.

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Mode coupling in large-diameter polymer-clad silica fibers

Cited by 25 publications

References 6 publications

Use of Analyte-Modulated Modal Power Distribution in Multimode Optical Fibers for Simultaneous Single-Wavelength Evanescent-Wave Refractometry and Spectrometry

Use of Analyte-Modulated Modal Power Distribution in Multimode Optical Fibers for Simultaneous Single-Wavelength Evanescent-Wave Refractometry and Spectrometry

Fiber-optic evanescent wave sensor with a segmented structure

Efficiency of pump absorption in gain-guided and index-antiguided (GG-IAG) fiber

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