U-shaped Plastic Optical Fiber Research Articles

Optoelectronic system for measuring the sugar content in citrus fruits

The color of oranges originates from carotenoids, which are natural pigments ranging from yellow to red color and is indicative of the sugar level and degree of ripeness. During the degreening process, the fruit quality can deteriorate, which is manifested as insufficient ripeness and sugar (sucrose) content. Therefore, in this study, we have designed a low-cost, easy-to-use optoelectronic system to measure the sugar content in orange and lemon juice. The system consists of a U-shaped plastic optical fiber (POF) and a visible multispectral sensor. The device identifies variation in the absorption of the evanescent field of the POF when it comes in contact with orange juice. The response of the multispectral sensor in the wavelength range of 450–650 nm is digitally captured, improving the efficiency and accuracy of the measurements. To validate the multispectral sensor measurements, the sugar contents are compared with those obtained using a visible spectrum analyzer and refractometer.

Ag@Fe3O4-coated U-shaped plastic optical fiber sensor for H2S detection

This work presents the fabrication of U-shaped plastic optical fiber (POF) sensors for hydrogen sulfide (H2S) detection, coated with Fe3O4 nanoparticles synthetized using the Pulsed Laser Ablation in Liquid (PLAL) technique. The Fe3O4 nanoparticles were synthetized in ultra-pure water and in silver nitrate solution, resulting in two colloidal samples with different morphological, optical, and structural properties. The Fe3O4 nanoparticles were coated onto one POF sensor, while the other sensor was coated with a nanostructure composed of Ag as the core and Fe3O4 as the shell (Ag@Fe3O4). The performance of both sensors was evaluated by exposing them to different concentrations of H2S and other gases such as CH4, H2, and CO2. All experiments were conducted at 25 °C. Results showed that the sensor coated with Ag@Fe3O4 was 12 times more sensitive to H2S compared to the sensor coated with Fe3O4, with a detection limit of 1 ppm and a rise time of 15 s. Moreover, the POF sensor coated with Ag@Fe3O4 presented high selectivity to H2S, making it a promising candidate for H2S detection in different applications. The sensor's performance was also evaluated with a relative humidity range of 20–90%, exhibiting a minimal 0.75% signal variation at 90% humidity.

U-shaped plastic optical fiber sensor for phosphate detection in water

U-shaped plastic optical fiber sensor for phosphate detection in water

The Influence of Geometric Shape on the Performance of Refractive Index Sensors Based on Plastic Optical Fibers: Simulations and Experimental Assessment

In this work, we present a comparative study on the influence of the geometric shape of plastic optical fiber (POF) sensors in their response to refractive index (RI) of external media. Three different geometric shapes were simulated using the finite-element method (FEM), one being a simple U-shaped POF sensor (FU) and the other two based on the same U shape but with one and two additional small curves in the fiber, FO1 and FO2, respectively, allowing for an increased exposure of the evanescent field. The results of simulations showed that the shapes of sensors FO1 and FO2 would allow for higher sensitivities compared to that of the simple U-shaped sensor FU and that FO2 would show an even higher sensitivity due to an increased evanescent field exposure enabled by the additional curves on its shape. A set of POF sensors were fabricated according to the designs simulated and then tested in several sucrose solutions corresponding to RI from 1.3330 to 1.4242. The POF sensors manufactured showed sensitivities (optical power loss) of 36%/RIU, 102%/RIU, and 217%/RIU for FU, FO1, and FO2, respectively, from air to pure water (RI 1.000 to 1.333), and 330%/RIU, 656%/RIU, and 904%/RIU for FU, FO1, and FO2, respectively, from pure water to sucrose solution (RI 1.333 to 1.381). The correlation between the results from simulations and experiments shows that POF sensors based on RI sensing, such as chemical sensors, gas sensors, and biosensors, can be significantly improved with small modifications in their shape design.

U-shaped plastic optical fiber sensor for scale deposition in hot spring water.

Fiber optic sensors for monitoring scale deposition in geothermal brine and hot spring water should be safe, easily fabricated, and readily disposable. These desired features already have been enhanced in plastic optical fibers (POFs) and U-shaped sensors for other applications. The present work reports a U-shaped POF sensor for CaCO3 scale deposition. The sensors were easily fabricated by thermally bending the bulk POF without removing the cladding. At the bend, the percentage of total internal reflection between the water and the POF surface is affected by the high refractive index of the CaCO3 deposit. The optical responses of the U-shaped sensor to CaCO3 formation were investigated in a mixture of calcium chloride dehydrate and sodium hydrogen carbonate using a white-light source and a spectroscopic detector. The sensor was responsive to CaCO3 formation on the sensor surface and was especially sensitive at small bending radii. The sensitivity was further enhanced by increasing the number of bends. Finally, the U-shaped POF sensor was applied to the monitoring of CaCO3 scale deposition in hot spring water sampled at Matsushiro, Japan.

Optical fiber sensor coated with copper and iron oxide nanoparticles for hydrogen sulfide sensing

This work presents the manufacture of optical sensors based on plastic optical fiber (POF) in U–shape and metallic nanoparticles for hydrogen sulfide (H2S) sensing. The manufacture of the sensors was divided into two stages, in the first stage the synthesis of oxidized metallic nanoparticles (copper oxide (CuONp) and iron oxide (FeONp)) were carried out with the Pulsed Laser Ablation in liquid. The nanoparticles were characterized to determine their optical properties, stability, morphology, structure, and size. The second stage consisted of the sensors’ development and their application in H2S sensing. Two sets of U-shaped POF sensors where manufactured, one with sensors covered with CuONp, and the other with sensors covered with FeONp. The results showed that all sensors were capable of detecting a gaseous mixture containing 200 ppm of H2S, and that the sensors coated with CuONp showed a higher sensitivity than the FeONp-covered sensors. However, the sensors manufactured with CuONp showed a non-reversible chemisorption behavior, while the sensors manufactured with FeONp exhibited reversible physisorption behavior. Comparatively, one of the sensors covered with FeONp was found to have a sensitivity seven times higher than the less sensitive sensor. In addition, that most sensitive sensor also showed a quick recovery time of less than 5 min and a rise time of around 6 min. Finally, the sensor was exposed to other reducing gases such as NH3 and CH4 and the results indicated that the developed sensor demonstrate selectivity to H2S. All sensors were tested at room temperature (25 °C).

Structure optimization of gold-sputtered side-polished U-shaped plastic optical fiber SPR sensor

PurposeThis study aims to optimize the structure of gold-sputtered U-shaped plastic fiber sensors.Design/methodology/approachA group of U-shaped Au-sputtered plastic optical fiber sensing probes with polishing angles of 45°, 90° and 135° is prepared.FindingsThe experimental results show that the spectral response and sensitivity of the sensor at 45°polishing angle is twice that of the sensor at 90°.Research limitations/implicationsDue to the limitations of laboratory temperature and equipment, the overall effect has not reached the ideal, but the expected effect has been obvious. Experiments also optimize the sensor.Practical implicationsOptical fiber sensing has always been an indispensable part of various fields.Social implicationsSensor optimization is of great help to the progress of technology and the development of science and technology.Originality/valueThe authors have no conflicts of interest to disclose.

Fiber optic system to measure adulteration in liquids using an RGB detection

In this paper, we propose a fiber optic system to measure the changes in the RGB composition of light in liquid solutions using a plastic optical fiber (POF) as an intrinsic sensor. The measurement system is composed of a 3 W white light-emitting diode as the light source, a 20 cm long U-shaped POF, and an RGB photodiode array that allows us to detect the changes in the RGB composition of the light propagating through the POF. The U-shaped POF has a length of 5 mm without coating, which remains in contact with the liquid solutions. The tests were performed with different concentrations of a mixture of tequila and water. The results obtained with the RGB photodiode array showed that the system has a resolution of 0.39 % and a color change sensitivity of 0.1, 0.6, and 0.4 8–bits/% of sample for red, green, and blue colors, respectively. These results will allow us to design a low-cost prototype to measure the amount of adulteration in liquids.

Plastic optical fiber sensor for temperature-independent high-sensitivity detection of humidity

A simple U-shaped plastic optical fiber evanescent-wave sensor was fabricated for temperature-independent highly sensitive detection of humidity. The sensing region of the sensor was subjected to five cycles of heating-cooling to improve temperature independence. The effects of the polyimide (PI) coating thickness, number of graphene oxide (GO) coating layers, and alternate PI-GO coating sequence were investigated to optimize sensitivity. The fabricated sensor exhibited high-temperature independence and good sensitivity of 0.17×10-2 (% relative humidity)-1 in the temperature range of 10°C to 70°C.

Surface Plasmon Resonance and Bending Loss-Based U-Shaped Plastic Optical Fiber Biosensors.

Escherichia coli (E. coli) is a large and diverse bacteria group that inhabits the intestinal tract of many mammals. Most E. coli strains are harmless, however some of them are pathogenic, meaning they can make one sick if ingested. By being in the feces of animals and humans, its presence in water and food is used as indicator of fecal contamination. The main method for this microorganism detection is the bacterial culture medium that is time-consuming and requires a laboratory with specialized personnel. Other sophisticated methods are still not fast enough because they require sending samples to a laboratory and with a high cost of analysis. In this paper, a gold-coated U-shaped plastic optical fiber (POF) biosensor for E. coli bacteria detection is presented. The biosensor works by intensity modulation principle excited by monochromatic light where the power absorption is imposed by predominant effect of either bending loss or surface plasmon resonance (SPR), depending on the gold thickness. Bacterial selectivity is obtained by antibody immobilization on the fiber surface. The biosensor showed a detection limit of 1.5 × 103 colony-forming units (CFU)/mL, demonstrating that the technology can be a portable, fast response and low-cost alternative to conventional methodologies for quality analysis of water and food.

Simulation of U-shaped plastic optical fiber ethanol sensor

The prediction of optical loss in different bending diameter of U-shaped POF sensor toward variation of ethanol’s refractive indices was investigated using ray-tracing method perform by Zemax software. It can provide information on how the propagation ray is perturbed by different bending diameter of U-shaped POF. There are five designs of POF models were pre-drawn with different bending diameter; 2.0cm, 2.5cm, 3.0cm 3.5cm and 4.0cm. From the results, U-shaped with 2.5 cm bending diameter has shown the most sensitive bending diameter as compared to the rest. Either with the presence of cladding layer or not the sensitivity detected was 0.014 x10 -4 Watts/Vol%.

Refractive index sensor based on a multi-notched plastic optical fiber.

We propose a plastic optical fiber (POF) with a multi-notched structure as a long-period grating for refractive index (RI) sensing. A new approach to modify the structure of POFs with enhanced RI sensitivity was carried out. The multi-notched structure was made on the surface of the fiber by pressing a thread rod against the POF. The RI sensing performances for straight and macro-bending (U-shaped) POFs with this structure were studied. It is found that the POF probes with straight multi-notched structures were not sensitive enough for RI measurements. After bending the multi-notched structure into U-shaped probes, the RI sensing performance was improved markedly. By altering the structural parameters, the RI sensing performance of the U-shaped POF probes with multi-notched structures were optimized, and the highest sensitivity of 1130%/RIU with a resolution of 8.44×10-4RIU in the RI range of 1.333-1.410 was obtained. In addition, the characteristic of the temperature dependence of the sensor was presented. The probe is a low-cost solution for RI sensing purpose, which has the features of simple structure, easy fabrication, compact size, and intensity modulation at visible wavelengths.

Experimental study of plastic optical fiber TNT sensor based on evanescence absorption

Here, the concentration of TNT was detected by using evanescent absorption method, U-shaped plastic optical fiber was used as sensor head and light transmit element. A high brightness blue light-emitting diode with spectrum centered at 470 nm was used as excitation source. The relationship between the transmitted light power of U-shaped sensor head and TNT concentration was linearly and the linear coefficient was 0.944. The system showed excellent reversibility when the sensor tested by alternately cycling between 0 and 25 mg/100 ml TNT solution in five cycles. The stability of the sensor head in 25 mg/100 ml TNT solution was also tested within two hours. The proposed sensor is a cost-effective alternative to traditional TNT sensors and provides a platform for other optically based sensors.

Study of the sensing characteristics of light emitting conjugated polymer MEH-PPV for nitro aromatic explosives

The sensing characteristics of light emitting conjugated polymer MEH-PPV for nitro aromatic explosives were studied in this paper. MEH-PPV was deposited on the surface of U-shaped plastic optical fiber (POF) using dip-coating techniques. The influences of MEH-PPV concentrations and bending radius of the U-shaped sensor heads on the sensitivity of the sensor were studied. The sensor was found to be most sensitive to TNT range from 0 to 4 mg/100 ml and the sensitivity was about 4 ng/ml. The limit of detections was around 1–10 ng/ml. It was also found that the conjugated polymer changes color from red to brownish black when the sensor head was put into TNT solution which provided high selectivity for sensing TNT at room temperature.

Study of TNT Sensor Based on Fluorescence Quenching of Conjugated Polymer MEH-PPV

A nitro aromatic explosives sensor based on fluorescence quenching was studied in this paper. U-shaped plastic optical fiber was used as sensor head and light emitting conjugated polymer MEH-PPV as fluorescence indictor. The light source was modulated sinusoidal to eliminate the external light disturbance. TNT quenching characteristics of fluorescence intensity were measured; When TNT concentration was lower than 10mg/ml, the relationship between fluorescence intensity and TNT concentration was linearly, when TNT concentration was higher than 10mg/100ml the obtained characteristics showed deviation from linear relation described by Stern-Volmer equation.

Study of nitro aromatic explosives sensor based on fluorescence quenching

A nitro aromatic explosives sensor based on fluorescence quenching was studied in this paper. U-shaped plastic optical fiber was used as sensor head and light emitting conjugated polymer MEH-PPV as fluorescence indictor. The light source was modulated sinusoidal to eliminate the external light disturbance. TNT quenching characteristics of fluorescence intensity was measured. When TNT concentration is lower than 10 mg/ml, the relationship between fluorescence intensity and TNT concentration is linearly, when TNT concentration is higher than 10 mg/100 ml the obtained characteristics showed deviation from linear relation described by Stern–Volmer equation.

基于U形塑料光纤的氧气传感器

基于U形塑料光纤的氧气传感器

基于U型塑料光纤和邻啡咯啉钌的溶解氧传感器

A dissolved oxygen (DO) sensor based on U-shape plastic optical fiber (POF) and dichlorotris (1, 10-phenanthroline) ruthenium ([Ru(dpp)3]2+) as an oxygen indicator was described. Fluorescence intensity and lifetime were measured when the sensor was soaked into a water bath blasted with air with varied O2/N2 ratios. The influence of Ru concentration, annealing time and U-shaped POF curve radius on the system sensitivity was also studied. A two-layer model was proposed to analyze the deviation from linear relation described by Stern-Volmer equation, and to explain the deviation and the dependence of the fluorescence on curvature of U-shape POF. By fitting the experimentally measured sub-linear relation of τ0/τ ratio versus oxygen concentration, the proportion of effectively sensitive layer and the Stern-Volmer coefficient can be evaluated to be f=0.59 and KSV=0.61 typically.