Detection of magnesium ion concentration using �ber coupler based displacement sensor with concave mirror target

Detection of magnesium ion concentration was successfully demonstrated using a fiber coupler based displacement sensor probe in conjunction with a concave mirror target. Analysis of peak voltage result, which was obtained by moving a sensing port displacement from a fixed concave mirror (CM) was found to be useful to detect a magnesium ion concentration, which is filled in between the probe and target. The proposed sensor is capable for measuring magnesium ion with variation of concentration 0–5%. The resolution of the sensor can be achieved at 0.2%. It was also observed that the use of CM with a longer focal length improves the sensitivity of the sensor. The high sensitivity, the small size, the ease fabrication process, and the bio-compatibility of the proposed device are appealing characteristics that makes it ideal for practical bio-sensing applications

Sodium nitrate (NaNO 3) sensor based on graphene coated micro�ber

We demonstrate the coating of graphene onto the silica optical microfiber sensor for improving sodium nitrate detection at room temperature. The graphene obtained from graphene- polylactic acid filament was coated onto the microfiber based on drop casting technique. In the proposed sensor, the graphene acts as cladding to interact with analyte as well as functions to trap either sodium cation or nitrate anion and increases the effective refractive index of the cladding. The proposed sensor shows a good sensitivity of 1.29 dBm/% and resolution of 0.049%. The sensitivity, repeatababilty and reversible response of the sensor were improved by the coating of graphene layer. The presence of graphene on the surface microfiber works as passive cladding and influence the light propagation through the microfiber

Tapered plastic optical fiber coated with ZnO nanostructures for the measurement of uric acid concentrations and changes in relative humidity

Simple sensors are proposed and demonstrated using a tapered POF coated with ZnO nanostructures for measurement of different concentrations of uric acid in de-ionized water and changes in relative humidity (RH). The sensor operates based on intensity modulation technique. The tapered POF were fabricated by etching method using acetone, sand paper and de-ionized water to achieve a waist diameter of 0.45 mm and tapering length of 10 mm. The tapered fiber were then coated with ZnO nanostructures using sol–gel immersion method on ZnO seeded and non-seeded fiber. As the concentration of the uric acid was varied from 0 ppm to 500 ppm, the output voltage of the sensor using tapered POF with seeded ZnO nanostructures increased linearly with a higher sensitivity of 0.0025 mV/ppm compared to 0.0009 mV/ppm for unseeded tapered POF coated with ZnO. Both samples showed almost similar linearity of the response cuves of about 98.2%. The tapered POF with ZnO nanostructures interact with uric acid due to strong electrostatic interaction resulting in the increase in response with the increasing concentration. In addition, the seeded ZnO nanostructure could significantly enhance the transmission of the sensor that is immersed in solutions of higher concentration. On the other hand, for both samples, the change in the intensity of the transmitted light of the tapered POF coated with ZnO nanostructures decreases linearly with relative humidity. The tapered POF with grown (seeded) ZnO provides better sensitivity at 0.0258 mV/% with a slope linearity of 95.48%. The ZnO nanostructures that are exposed to an environment of humidity causes rapid surface adsorption of water molecules and changes in optical properties. The tapered POF coated with ZnO nanostructures using the seeding technique causes an increase in both effective RI of surrounding medium and absorption coefficient of the ZnO nanostructures surfaces and leads to larger leakage of light. Results show that tapered POF with seeded ZnO nanostructures enable to increase the sensitivity of fiber for uric acid detection as well as relative humidity. The proposed sensors provide numerous advantages such as simplicity of design, low cost of production, higher mechanical strength and easier to handle compared to silica fiber optic

Fiber bundle sensor for detection of formaldehyde concentration in fish

We experimentally demonstrate an optical fiber bundle based sensor for measuring formaldehyde concentration in fish. We show that when contaminated fish samples are shined with red laser light with about 630 nm wavelength, the intensity of the backscattered radiation increases linearly with respect to the formaldehyde concentration. Our sensor has a simple architecture, it exhibits good sensitivity, linearity and stability and it has been tested for formaldehyde concentrations ranging from 3% to 21%. Our sensor allows non-destructive, on-site measurements and will have applications towards the development of all-optical cheap and portable sensors for detection of pollutants and toxic chemicals in the food industry and in the agriculture sector, being potentially suitable for measurements in the field

Fiber bundlesensorfordetectionofformaldehydeconcentrationinfish

We experimentallydemonstrateanopticalfiberbundlebasedsensorformeasuringformaldehydeconcentrationinfish.Weshowthatwhencontaminatedfish samples areshinedwithredlaserlightwithabout630nmwavelength,theintensityofthebackscatteredradiationincreaseslinearlywithrespecttotheformaldehyde concentration. Oursensorhasasimplearchitecture,itexhibitsgoodsensitivity,linearityandstabilityandithasbeentestedforformaldehydeconcentrationsranging from 3%to21%.Oursensorallowsnon-destructive,on-sitemeasurementsandwillhaveapplicationstowardsthedevelopmentofall-opticalcheapandportable sensors fordetectionofpollutantsandtoxicchemicalsinthefoodindustryandintheagriculturesector,beingpotentiallysuitableformeasurementsinthefield