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Bend radius

About: Bend radius is a research topic. Over the lifetime, 3303 publications have been published within this topic receiving 35415 citations. The topic is also known as: minimum bend radius.


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Journal ArticleDOI
TL;DR: In this article, the amplitude modulation caused by the variation in the radius of a concave micro-mirror crafted into the end of an SMF optical fiber is investigated, which can be used in a wide range of applications.
Abstract: This article presents a fibre-optic sensor that measures temperature and pressure. Its operating principle is based on the amplitude modulation caused by the variation in the radius of a concave micro-mirror crafted into the end of an SMF optical fibre. In fact, a micro-cavity engraved into the end of the fibre by selective chemical etching is filled with a PDMS (Polydimethylsiloxane)-type polymer. Due to surface tension, the polymer micro-drop takes on a hemispheric shape characterised by a certain radius. After polymerisation in an oven at 100 °C for one hour, the hemispheric micro-drop is coated with a thin layer of gold using the vacuum evaporation technique. Typically, concave micro-mirrors can be obtained with bend radii of between 10μm and 30μm. Under the action of a temperature gradient or a variation in pressure, the thickness of the PDMS changes and causes a variation in the bend radius of the micro-mirror. As a result, the light intensity guided by the optical fibre and reflected by the micro-mirror is modulated by the variation in its bend radius. In this configuration, the sensor has a thermo-sensitivity of – 0.08dB/°C with a resolution of 0.13 °C in a range of between 20 °C and 100 °C. It also has a pressure sensitivity of 0.11dB/bar between 10 and 20 bars. The measurements are taken by a reflectometer (OTDR). In addition, the experimental results have been validated by theoretical modelling. This sensor is relatively simple to make and can be used in a wide range of applications, in particular biomedical and industrial ones.

14 citations

Journal ArticleDOI
TL;DR: In this article, an approximate and simple method for predicting the field profile in a curved dielectric waveguide of rectangular cross section is described, and it is shown that the transverse field can be approximated inside the guide by the Airy function of the first kind.
Abstract: An approximate and simple method for predicting the field profile in a curved dielectric waveguide of rectangular cross section is described. For a single-mode propagation, it is shown that the transverse field can be approximated inside the dielectric guide by the Airy function of the first kind and that the radial attenuation constant is a function of the bending radius outside the guide. Experimental verification of the theoretical results is included.

14 citations

Journal ArticleDOI
01 Apr 1997
TL;DR: In this paper, the scalar Helmholtz equation for a step-index planar waveguide with a constant bend radius and assuming a bend radius large in comparison to the core half-width yields a differential equation whose solutions can be written in terms of Airy functions.
Abstract: Conformally transforming the scalar Helmholtz equation for a step-index planar waveguide with a constant bend radius and assuming a bend radius large in comparison to the core half-width yields a differential equation whose solutions can be written in terms of Airy functions. A correct expansion of the leaky mode field in terms of these Airy functions and matching the field and its derivative across boundaries yields an eigenvalue equation whose complex roots give the leaky mode propagation constant and bend loss directly. This allows a second-order Taylor series expansion for the bend loss as a function of wavelength over the spectrum of a pulse to be determined. A comparison between bend loss for a cw wave and a pulse with the same carrier frequency is made.

14 citations

Proceedings ArticleDOI
TL;DR: In this paper, the attenuation characteristics of 2μm thick silver-coated waveguides with 99% reflective inner surface were measured as a function of wavelength, bore diameter, bending angle and bend radius.
Abstract: Low-loss, hollow, flexible, metal-coated waveguides were designed and fabricated for the maximal transmission of terahertz radiation. Since recent terahertz skin, colon, and breast cancer studies showed a contrast between normal and diseased tissues between 500 to 600GHz frequencies, flexible metal-coated waveguides with various bore diameters were studied at both 584GHz and 1.4THz frequencies for endoscopic applications. Attenuation characteristics of 2μm thick silver-coated waveguides with 99% reflective inner surface were measured as a function of wavelength, bore diameter, bending angle and bend radius. Though the theoretical attenuation coefficient in metal-coated waveguide varies directly as square of wavelength, the propagation loss was found to be smaller at higher wavelengths. This study demonstrates that flexible waveguides with bore diameters less-than 10λ preserve the linearly polarized mode and hence exhibit low bending losses even at smaller bend radii. Also, in contrast to the lower propagation losses in larger bore tubes, the analysis shows higher transmission in smaller bore tubes at larger bending angles. Finally, the dual-frequency investigation of bending and modal characteristics confirms the feasibility of using these metal-coated flexible waveguides at various terahertz frequencies, to obtain low transmission losses even at greater flexures, in addition to the Gaussian mode preservation.

14 citations

Journal ArticleDOI
TL;DR: In this article, the influence of internal pressure, operation time and shape imperfections of a pipe bend on stress-strain redistributions and creep-fatigue crack growth rates was investigated using FE-analysis and experiments at elevated temperature.

14 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202365
2022172
202181
2020112
2019135
2018153