Built on a design developed from an advanced mathematical model, a practical fiber optic sensor, which is an analog of the familiar ‘hot-wire’ wind velocity monitor is developed, as an intrinsically-safe sensor device for coal mining monitoring applications. The underpinning optical fiber-based principle used is the shift in the center wavelength of a Fiber Bragg Grating which is cooled by the gas flowing over it and the device sensitivity found was determined to be ~1370pm per unit m/s wind velocity (in the range of 0-0.57 m/s), ~109pm per unit m/s in the range 0.57-2.26 m/s and ~33pm per unit m/s in the range of 2.26-5.66 m/s. In this paper, the factors that influence the device response time, such as the sensor probe surface heat transfer coefficient, wind (gas) velocity and pump power have been investigated in the laboratory. It was found that the greater the surface dissipation factor of the sensor, the shorter the response time, furthermore, the response time was observed to decrease as the wind velocity increased. A method of further shortening sensor response time using wind speed variation slope is proposed.
Surface Enhanced Raman Scattering (SERS) is typically observed with the substrate in a liquid medium and it has been proposed as a promising technique for detecting low levels of pollutants in liquids. The design and fabrication of an optical fibre SERS sensor based on Au nanoparticles (Au-NPs), which is self-assembly immobilized onto the end surface of an optical fibre is described. Two toxic materials, Rhodamine 6G (R6G) and crystal violet were analysed using this optical fibre SERS sensor combined with portable Raman spectrometer. Our proposed fabrication and analytical method offers a rapid, cheap and disposable trace detection capability for toxic materials in the field.
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