Temperature sensing using CdSe quantum dot doped poly(methyl methacrylate) microfiber.

This work describes noncontact temperature measurements using wavelength shifts of CdSe quantum dot (QD) doped poly(methyl methacrylate) microfiber. The sensor is fabricated using a drawing method by bridging two tapered single mode fibers with a polymer microfiber (PMF) approximately 3 µm in diameter. A set of a PMF section with and without the doping of the CdSe-ZnS core-shell QD was applied as sensing probes and used to measure temperatures over the range of 25°C-48°C. The experimental results show that the doped PMF is able to achieve a higher performance with a reasonably good sensitivity of 58.5 pm/°C based on the wavelength shifting, which is about 18 times that of the undoped PMF temperature sensitivity. The proposed sensor showed a linear temperature sensing range that matches well with the physiologically relevant temperatures. Moreover, these results open the way for long-term and high-stability realization of temperature sensing optical fibers.

Temperature compensation in determining of Remazol black B concentrations using plastic optical fiber based sensor.

In this study, the construction and test of tapered plastic optical fiber (POF) sensors, based on an intensity modulation approach are described. Tapered fiber sensors with different diameters of 0.65 mm, 0.45 mm, and 0.35 mm, were used to measure various concentrations of Remazol black B (RBB) dye aqueous solutions at room temperature. The concentrations of the RBB solutions were varied from 0 ppm to 70 ppm. In addition, the effect of varying the temperature of the RBB solution was also investigated. In this case, the output of the sensor was measured at four different temperatures of 27 °C, 30 °C, 35 °C, and 40 °C, while its concentration was fixed at 50 ppm and 100 ppm. The experimental results show that the tapered POF with d = 0.45 mm achieves the best performance with a reasonably good sensitivity of 61 × 10(-4) and a linearity of more than 99%. It also maintains a sufficient and stable signal when heat was applied to the solution with a linearity of more than 97%. Since the transmitted intensity is dependent on both the concentration and temperature of the analyte, multiple linear regression analysis was performed to combine the two independent variables into a single equation. The resulting equation was then validated experimentally and the best agreement between the calculated and experimental results was achieved by the sensor with d = 0.45 mm, where the minimum discrepancy is less than 5%. The authors conclude that POF-based sensors are suitable for RBB dye concentration sensing and, with refinement in fabrication, better results could be achieved. Their low fabrication cost, simple configuration, accuracy, and high sensitivity would attract many potential applications in chemical and biological sensing.

Fibre optic sensors for selected wastewater characteristics.

Demand for online and real-time measurements techniques to meet environmental regulation and treatment compliance are increasing. However the conventional techniques, which involve scheduled sampling and chemical analysis can be expensive and time consuming. Therefore cheaper and faster alternatives to monitor wastewater characteristics are required as alternatives to conventional methods. This paper reviews existing conventional techniques and optical and fibre optic sensors to determine selected wastewater characteristics which are colour, Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD). The review confirms that with appropriate configuration, calibration and fibre features the parameters can be determined with accuracy comparable to conventional method. With more research in this area, the potential for using FOS for online and real-time measurement of more wastewater parameters for various types of industrial effluent are promising.