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The mode coupling in a graded-index polymer photonic crystal fiber (GI PPCF) with a solid core has been investigated using the Langevin equation. Based on the computer-simulated Langevin force, the Langevin equation is numerically integrated. The numerical solutions of the Langevin equation align with those of the time-independent power flow equation (TI PFE). We showed that by solving the Langevin equation, which is a stochastic differential equation, one can successfully treat a mode coupling in GI PPCFs, which is an intrinsically stochastic process. We demonstrated that, in terms of effectiveness, the Langevin equation is preferable compared to the TI PFE. The GI PPCF achieves the equilibrium mode distribution (EMD) at a coupling length that is even shorter than the conventional GI plastic optical fiber (POF). The application of multimode GI PCFs in communications and optical fiber sensor systems will benefit from these findings. [ABSTRACT FROM AUTHOR]

We propose a spectral filter based on a plastic optical fiber with micro-holes as a low-cost, robust, and highly reproducible spectral filter. The spectral filter is explored for two configurations: a fiber extended in a straight line and a fiber optic loop mirror scheme configuration. The transmission traces indicate a spectral blue shift in peak transmission, at 587 nm, 567 nm, 556 nm, and 536 nm for zero, one, two, and three holes in the fiber, respectively. The filter exhibits a bandpass period of approximately 120 nm. Additionally, we conduct a comparison of the transmission with holes separated by distances of 1 cm and 500 μm. The results demonstrate that the distance between holes does not alter the spectral transmission of the filter. In the case of the fiber loop mirror configuration, we observe that the bandpass can be adjusted, suggesting the presence of multimode interference. Exploring variations in the refractive index within the holes by filling them with glucose solutions at various concentrations, we determine that the filtering band and spectral shape remain unaltered, ensuring the stable and robust operation of our spectral filter. [ABSTRACT FROM AUTHOR]

A new type of human immunoglobulin G (IgG) sensors based on the surface plasmon resonance (SPR) in the low refractive index (RI) plastic optical fiber (POF) and an antibody immobilization method is presented. A 50-nm-thick gold film was formed on the polished D-shaped fiber surface by magnetron sputtering. The RI response of the POF sensor is 30 049.61 nm/RIU, which is 26.5 times higher than that of single mode fiber (SMF) SPR sensors. The proposed SPR biosensor can be developed by simple and rapid modification of the gold film with 11-mercapto undecanoic acid (MUA). Upon immobilization of the goat anti-human IgG antibody, the resonance wavelength shifts by 11.2 nm. The sensor can be used to specifically detect and quantify the human IgG at concentrations down to 245.4 ng/mL with the sensitivity of 1.327 7 nm per µg/mL, which offers an enhancement of 12.5-fold compared to that of the conventional SMF based SPR sensors. The proposed device may find the potential applications in the case of use at the point of care. [ABSTRACT FROM AUTHOR]

This article compares the performance of U and coil-shaped fiber optic sensors for the detection of fluoride in water. Low-cost and simple-to-use U-shape and coil-shape evanescent wave fiber optic sensors have been designed and developed for in-situ detection of fluoride in water. The sensitivities of coil and U-shaped sensors are found to be 0.1418 O.D./ppm and 0.1409 O.D./ppm, respectively, with linear regression coefficients (R2) of 98.25% and 98.20%. [ABSTRACT FROM AUTHOR]

Using the dip-coating technique, a photo-anode based on a plastic optical fiber (POF) was coated with a mixture of titanium oxide nanoparticles (TiO2:Ti4O7). The semiconductor-coated material was prepared so that UV radiation fed into the fiber would escape along its path, photo-exciting the electrically polarized semiconductor film and producing oxidant species capable of degrading pollutant chemicals in aqueous solution. The photoelectrode was developed to evaluate the potential degradation of organic pollutants in aqueous solutions, and for this purpose, methyl red was used to assess the photo-anode performance under photocatalysis, electrocatalysis, and photo-electrocatalysis processes. The results revealed that, as expected from the specific properties of TiO2 and Ti4O7, the TiO2:Ti4O7-coated POF substrates showed a synergistic effect when UV light and electrical polarization are applied. The main purpose of using POFs instead of conventional SiO2 fibers is that the former implies substantially lower cost and mechanical flexibility, which will result in the future novel photo-electrochemical arrangements for water treatment. [ABSTRACT FROM AUTHOR]

In this work, a surface plasmon resonance (SPR) biosensor based on a spoon-shaped waveguide combined with an estrogen receptor (ERα) was developed and characterized for the detection and the quantification of estradiol in real water samples. The fabrication process for realizing the SPR platform required a single step consisting of metal deposition on the surface of a polystyrene spoon-shaped waveguide featuring a built-in measuring cell. The biosensor was achieved by functionalizing the bowl sensitive surface with a specific estrogen receptor (ERα) that was able to bind the estradiol. In a first phase, the biosensor tests were performed in a phosphate buffer solution obtaining a limit of detection (LOD) equal to 0.1 pM. Then, in order to evaluate the biosensor's response in different real matrices related to aquaculture, its performances were examined in seawater and freshwater. The experimental results support the possibility of using the ERα-based biosensor for the screening of estradiol in both matrices. [ABSTRACT FROM AUTHOR]

We report the design and testing of a sensor pad based on optical and flexible materials for the development of pressure monitoring devices. This project aims to create a flexible and low-cost pressure sensor based on a two-dimensional grid of plastic optical fibers embedded in a pad of flexible and stretchable polydimethylsiloxane (PDMS). The opposite ends of each fiber are connected to an LED and a photodiode, respectively, to excite and measure light intensity changes due to the local bending of the pressure points on the PDMS pad. Tests were performed in order to study the sensitivity and repeatability of the designed flexible pressure sensor. [ABSTRACT FROM AUTHOR]

• A fiber optic respiratory sensor based on optical fibers and silicon tube is proposed. • Static and accurate performance testing of fiber optic respiratory sensors is proposed. • The proposed respiratory sensors show high sensitivity and wide measurement range detection. An optical fiber sensor based on the principle of intensity modulation is proposed, which is composed of plastic optical fibers and silicone tubes. The displacement measurement is achieved by stretching the optical fibers to cause changes in the angle between the end faces, resulting in changes in the coupling efficiency between the end faces. To address the challenges in the performance calibration of fiber optic respiratory sensors, it is proposed to convert the dynamic characteristics measurement of the respiratory sensor into the static performance analysis of the displacement sensor, so as to obtain the characteristics such as sensitivity, linearity, and repeatability, etc. It is further proposed to use a stepper motor to simulate the periodic stretching process of the optical fibers caused by the respiratory process, enabling the analysis of frequency measurement accuracy under different respiratory strengths. Simulation and experimental results demonstrate that the proposed sensor has high linearity, good repeatability, high sensitivity, and a wide measurement range. It can accurately measure respiratory frequency and display amplitude information, providing comprehensive information for respiratory monitoring. [ABSTRACT FROM AUTHOR]

• An optical fiber daylighting system (OFDS) is implemented for an indoor farm, which allows addressing costly issues and achieving high efficiency. • An optimal design of the OFDS along with the various distances between the focal area and the optical fiber. • A concentration ratio of 140, optical efficiency of ∼19 % in simulation and ∼16 % in practice is demonstrated. • Energy saving can reach 54.3% on a sunny day and 38.9% on a cloudy day in an outdoor test. • Using the proposed OFDS helps the plant to grow better compared to using only LED. Optical fiber daylighting technology offers an effective path to deliver sunlight to an indoor farm that requires high energy consumption for illumination and a total visible spectrum for plant growth. However, the high cost of this technology can be seen as a drawback. In this study, the optimized daylighting system based on plastic optical fiber for indoor farm application is devised toward large-scale illumination with high efficiency and low cost. The proposed system comprises of a Fresnel lens array as a sunlight concentrator and plastic optical fiber bundles as a light transportation medium. Rather than previously common designs, we investigated the concentration properties of a non-imaging optics device – the Fresnel lens to find the optimal configuration of the system. Optimizing concentration ratio, optical efficiency, and overheating of an optical fiber daylighting system (OFDS) for the indoor farm application is carried out by simulation (LightTools software) and verified by experiments. The system design allows replacing the costly and sophisticated heat dissipation in conventional OFDS with only a UV-IR filter. The OFDS prototype is fabricated and tested in outdoor conditions. Results show that the proposed system archive concentration ratio of 140, the optical efficiency of ∼19 % by simulation, and ∼16 % by practice. Daylighting performance investigation on the installation of the prototype in the indoor farm demonstrates that energy saving can reach 54.3 % on a sunny day and 38.9 % on a cloudy day. Using proposed OFDS helps the plant to grow better than using LED only. Reliability tests and cost analyses show that our results provide an essential breakthrough for the application and commercialization of large-scale optical fiber daylighting technology for indoor agriculture. [ABSTRACT FROM AUTHOR]

Optimization of light source wavelength for ammonia detection in surface water is presented in this work. For the ammonia detection, the surface water sample is mixed with sodium chloride and nessler reagent, whereas the sensor head consists of unclad plastic optical fiber. The unclad region has a length of 1 cm and the cladding is removed by immersing it in acetone solution. Experimental results indicate that the output light intensity of the sensor has linear relationship with the ammonia concentration. At the wavelength of 510 nm, the output light increases linearly as the ammonia concentration varies from 0.07 mg/L to 8.97 mg/L. At the same wavelength, the proposed sensor achieves the sensitivity of 0.0139 (mg/L)-1, accuracy of 99.59% and resolution of 0.72 µg/L. The analysis of light source wavelength reveals that a wavelength range from 450 nm to 580 nm produces the optimized performances. Within this wavelength range, the proposed sensor achieves sensitivity of higher than 0.01 (mg/L)-1, accuracy of higher than 99% and resolution of less than 1 µg/L. [ABSTRACT FROM AUTHOR]

This paper presents a novel in‐home communication system employing plastic optical fibers (POFs) acting both as transmission medium and access point for wireless links to user devices, hence no separate luminaires or optical–electrical–optical conversions is required. All active devices, such as lasers/detectors, can be remotely placed from the room ceilings, resulting in fully passive optical front‐ends, which is beneficial for maintenance and upgrading. We approach two concepts, the first aims to realize small but high‐capacity hotspots in a room, the second creates larger coverage areas to increase the number of users and allow user's mobility. The wavelength division multiplexing concept is used to maximize the wireless throughput and to serve different wireless access points on the ceilings from a single POF feeder. A transmission link comprising eye‐safe transceivers, 1‐mm core diameter step‐index POF, and free space link, achieving multi‐gigabit throughputs using spectral efficient modulation formats, is demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, a U-shaped probe with a curvature diameter of half a centimeter was implemented using plastic optical fibers. A layer of the outer shell of the fibers was removed by polishing to a D-section. The sensor was tested by immersing it in a sodium chloride solution with variable refractive index depending on solution concentrations ranging from 1.333 to 1.363. In this design, the sensor experienced a decrease in its intensity as the concentration of the solution increased. The next step The sensor was coated with a thin layer of gold with a thickness of 20 nm, and the sensor was tested with the same solutions which resulted in a shift in wavelengths where the shift in wavelength was 5.37 nm and sensitivity 179 nm / RIU. To study the effect of the thickness of the film, it was coated with a second layer of gold to make the total thickness 30 nm. The results showed an improvement in the sensitivity with increasing the thickness of the coating, to become 466.66 nm / RIU and the wavelength shift was 14 nm. [ABSTRACT FROM AUTHOR]

• Development of a novel D-shaped plastic optical fiber sensor by using a dry etching method. The sensing region was coated with functionalized MWCNTs to produce strong evanescent waves. • Several experiments were conducted to investigate how plain and MWCNTs coated D-shaped sensor responds to mercury in aqueous solution ranging from 0 to 5 ppm. • A thin layer of MWCNTs improves the sensitivity of the sensor by improving the evanescent wave around the fiber, resulting in better interaction with the analyte. • The performance of the developed sensor in terms of sensitivity is 7.33 %/ppm and response/recover time is 6.3 s and 13 s respectively. Which is expected to play an important role in the industrial and health sectors to protect human health from detrimental effects due to high concentrations of mercury. Heavy metal pollutants in rivers and water catchments are one of the problems faced by many developing countries as they may result in health issues among their people. A proper sensing mechanism is required to ensure the quality of water. In this research, we propose a simple, low cost, and highly sensitive D-shaped plastic optical fiber (POF) sensor layered with functionalized multi-walled carbon nanotubes (MWCNTs) for the detection of mercury in water. The sensor underwent interrogation across a range of mercury concentrations at room temperature. Numerous methods of characterization have been employed to explore the intricate structural attributes of the sensing layer to verify that the nanocomposite surface layer is functionalized with minimal disruption to the nanotubes. The experimental results revealed that the coated sensor displayed swift response and recovery time of 6.3 s and 13 s respectively when tested with the dynamic mercury concentration range (0 to 5 ppm). Moreover, it exhibited a relative absorbance of 7.33 %/ppm, which is approximately four times higher than the plain sensor and a limit of detection (LOD) of 0.1 ppm. The sensor has the potential to be transformed into an on-site, portable, real-time optical sensor for the detection of mercury ions in drinking water, offering high sensitivity and fast data acquisition. [ABSTRACT FROM AUTHOR]

The proper measurement of plantar pressure during gait is critical for the clinical diagnosis of foot problems. Force platforms and wearable devices have been developed to study gait patterns during walking or running. However, these devices are often expensive, cumbersome, or have boundary constraints that limit the participant's motions. Recent advancements in the quality of plastic optical fiber (POF) have made it possible to manufacture a low-cost bend sensor with a novel design for use in plantar pressure monitoring. An intensity-based POF bend sensor is not only lightweight, non-invasive, and easy to construct, but it also produces a signal that requires almost no processing. In this work, we have designed, fabricated, and characterized a novel intensity POF sensor to detect the force applied by the human foot and measure the gait pattern. The sensors were put through a series of dynamic and static tests to determine their measurement range, sensitivity, and linearity, and their response was compared to that of two different commercial force sensors, including piezo resistive sensors and a clinical force platform. The results suggest that this novel POF bend sensor can be used in a wide range of applications, given its low cost and non-invasive nature. Feedback walking monitoring for ulcer prevention or sports performance could be just one of those applications. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to analyze the transmission characteristics of a long-period grating (LPG) fabricated on plastic optical fibers (POFs) and its refractive index (RI) sensing. Design/methodology/approach: The geometric optic method is used to analyze the factors affecting the transmission characteristics of an LPG on POFs. The RI sensing performances of unbent LPGs and U-bent LPGs fabricated on POFs with different diameters are evaluated experimentally. Findings: This study shows that the transmission loss caused by LPG strongly depends on the structural parameters of LPG and the environmental RI. For the unbent LPG, the highest RI sensitivity of 1,015%/RI unit (RIU) was obtained in the RI range of 1.33–1.45. For the U-bent LPG without cladding, the highest RI sensitivities of 1,007 and 559%/RIU are obtained in the RI ranges of 1.33–1.40 and 1.40–1.45, respectively. Originality/value: A geometric optic method is used to analyze the transmission characteristics for an LPG on POFs, and the RI sensing of the LPGs are studied experimentally. The results show the LPG has a good RI sensing performances and is with the features of low-cost, simple structure and easy fabrication. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The light-transmitting cementitious materials (LTCM) in a homemade device were produced with plastic fiber-optics, luminescent powder, reflective powder, and cement. The mechanical strength of LTCM was greatly enhanced by the incorporation of optical fiber, luminescent powder, and reflective powder. The maximum increase of the 3-day, 7-day, and 28-day compressive strengths and 3-day flexural strength of the LTCM are 15.33, 19.05, 13.10, and 5.15 MPa, respectively. The optical test results show that the absorption rate increases slowly with the increasing wavelength in the visible light range, and the 7 × 7 fiber arrangement mode obtains the best average absorption rate up to 0.58%. The reflectivity rate reached the peak values of 40.9, 37.2, and 29.2% in the range of the green light wavelength with 5 × 5, 6 × 6, and 7 × 7 of the fiber meshes. The transmittance rate of concrete with 5 × 5, 6 × 6, and 7 × 7 jumps to 0.28, 0.82, and 2.0% at the wavelength of 400 nm and then remains stable with the increase of the wavelength. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Featured Application: The work shows the development of an optical chemosensor based on a synthetic receptor, a molecularly imprinted polymer, for a furanic compound, 2-furaldehyde, with a good possibility of application in liquid samples, even very complex, and with high refractive index as a vegetable oil. This opens the way for the wide application of this sensing technique on site and in matrices of high industrial interest. Optical chemosensors with surface plasmon resonance (SPR) transduction are widely employed, even in complex environments, such as those outside the laboratory. In this context, not only the chemical nature but also the physical form of the receptor layer is particularly relevant. Synthetic receptors as molecularly imprinted polymers (MIPs) are well suited. This is demonstrated here in the case of an SPR sensor platform based on a multimode plastic optical fiber, which is very promising for on site application due to the low dimensions and low cost. A specific MIP was used as the receptor, with high affinity for the substance to be determined, 2-furaldehyde, in water. Here, a medium of high refractive index, i.e., vegetable oil, was considered because of the high interest for its determination in industrial diagnostics. The effects of the MIP layer thickness and the washing extent on the quality of the analytical signal were investigated. Better spectra were generated at the thinner MIP layer, while a lower detection limit is reached with extended washing. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• A fully new scheme of the daylighting using optical-fiber-less design and hybrid system. • Aiming to guide light deeply and efficiently for a given multi-storey building. • The optical efficiency and energy saving can reach 63.7 % and 46.5%, respectively. In this study, the fully new scheme of the daylighting system is devised and a few avenues are proposed toward large scale illumination area with the highly efficient luminous flux and modest cost. Rather than a previously common design, consisting of a sole system, we work out two subsystems for a generic daylighting system: outdoor and indoor subsystems. For the outdoor subsystem, aiming to guide light deeply and efficiently for a given multi-storey building, we first capitalize on a simple design of two mirrors to collect the sunlight and transport it in free-space, which negligibly penalizes the optical loss. To guide light to each particular area inside building, we further propose two options for the indoor subsystem taking into consideration between cost and performance: first with the Fresnel lens + circular plastic optical fiber (POF) bundle and second with the waveguide concentrator + flat POF bundle. The quantitative assessment unravels that the optical efficiency of the latter is higher than that of the former, 63.7 % vs 48.7 %. Still, the real implementation of the Fresnel lens + circular POF is more prone and we indeed demonstrate a principle-of-concept system. Such design also preferably implements with a LED panel, in an embodiment of a so-called hybrid daylighting system, to grant light in overcast and night-time situations. This proposed daylighting system also enables exceptional merit in calculated energy saving, up to roughly 46.5% in a year with sunlight condition as in Ho Chi Minh City (Vietnam), as electrical light is used properly and barely. All things taken into account, this approach indicates a likely perspective for fostering a new generation of the daylighting system that making use of sparingly optical fiber. [ABSTRACT FROM AUTHOR]

A chemical optical fiber sensor based on surface plasmon resonance (SPR) was developed and implemented using multimode plastic optical fiber. The sensor is used to detect and measure the refractive index and concentration of various chemical materials (Urea, Ammonia, Formaldehyde and Sulfuric acid) as well as to evaluate the performance parameters such as sensitivity, signal to noise ratio, resolution and figure of merit. It was noticed that the value of the sensitivity of the optical fiber-based SPR sensor, with 60nm and 10 mm long, Aluminum(Al) and Gold (Au) metals film exposed sensing region, was 4.4 μm, while the SNR was 0.20, figure of merit was 20 and resolution 0.00045. In this work a multimode plastic optical fiber with a core diameter of 980 μm, fluorinated polymer cladding of 20 μm and a numerical aperture of 0.51 was used. [ABSTRACT FROM AUTHOR]

• Respiratory sensor based on two segments of plastic optical fibers and a clamp based on the 3D printing technology is proposed. • The experiment demonstrates the scheme's capability to detect a broad range of stable respiratory frequencies and weak signals. • An automatic multi-scale peak detection algorithm is utilized to achieve real-time display of transient respiratory rate, which enables the timely feedback of apnea and abnormal signals. A respiratory signal sensing scheme based on plastic optical fiber and smartphone is proposed. Respiratory signals are achieved by detecting the changes in abdominal circumference caused by the inhalation and exhalation of air from the lungs during breathing. A flexible clamp is prepared based on the 3D printing technology and the changes in abdominal circumference are leading to the lateral distance variation between the end face of the two plastic optical fibers in the clamp. The experiment demonstrates the scheme's capability to detect a broad range of stable respiratory frequencies and weak signals. Finally, an automatic multi-scale peak detection algorithm is utilized to achieve real-time display of transient respiratory rate, which enables the timely feedback of apnea and abnormal signals. The proposed respiratory sensing system provides an efficient, accurate, convenient and low-cost solution for human physiological signal monitoring. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to optimize the structure of gold-sputtered U-shaped plastic fiber sensors. Design/methodology/approach: A group of U-shaped Au-sputtered plastic optical fiber sensing probes with polishing angles of 45°, 90° and 135° is prepared. Findings: The 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/implications: Due 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 implications: Optical fiber sensing has always been an indispensable part of various fields. Social implications: Sensor optimization is of great help to the progress of technology and the development of science and technology. Originality/value: The authors have no conflicts of interest to disclose. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Langevin equation is used to investigate the state of mode coupling in step-index plastic optical fibers under varied temperature. The numerical integration of the Langevin equation is based on the computer-simulated Langevin force. The solution matches the experimental data reported previously. We find that elevated temperatures of plastic optical fibers are strengthening mode coupling. We show that, solving the Langevin equation (stochastic differential equation), one can treat a mode coupling in heated multimode step-index plastic optical fibers, which is a result of fiber's intrinsic random perturbations. [ABSTRACT FROM AUTHOR]

In this paper, we have proposed a way for reducing the dispersion level in plastic optical grating fiber by optimizing the grating-coupling strength (ξ) numerically. The effects of average refractive index (δn) and temperature (T) variation on the dispersion properties are investigated. Results show that, for reducing the dispersion level, the ξ parameter should be optimized and the amplitude of the δn needs to be reduced. Also results show that the dispersion due to the wavelength shift induced by the temperature variation will be eliminated by operating at high ξ value. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) sensors are attracting considerable attention for their use in biomaterials inspection, chemical detection, and physical testing. This paper presents an experimental investigation on an SPR-based plastic optical fiber (POF) refractive index sensor. The sensor was fabricated using a POF in which some of the core was removed by polishing and a 40 nm gold thin film was deposited on the polished surface. The refractive index sensor was used to measure analytes with refractive indices in the range from 1.330 to 1.456. Two windows, an SPR window and a refraction window, were observed in the optical transmission spectrum, where the SPR window from 650 to 700 nm and the refraction window from 760 to 780 nm show a strong linear relationship between the SPR wavelength and the normalized transmitted intensity. Sensitivities of 328 nm/RIU and -0.83/RIU (RIU, refractive index unit) were achieved for the SPR and refraction windows, respectively. We also discuss the merits of both windows for biomolecule sensing. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Kufa - Physics is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Population growth and urbanisation have resulted in exploitation of natural resources, anomalous climate change and environmental pollution. Thus, there is a need for the development of new construction techniques that will not only ensure the preservation of natural resources but at the same time will focus in making a building that is energy efficient and environment friendly. Light transmitting concrete aims to meet such requirement which helps in bringing the minimisation of artificial energy usage by directly allowing the sunlight to project through a concrete material. This paper deals with the study of mechanical and optical properties of light transmitting concrete produced by the inclusion of 2mm diameter plastic optical fiber with four different densities in a concrete cube of dimension 150mmx150mmx150mm. The experimental results show that mechanical strength of concrete mixes containing plastic optical fiber (7x7) increases by 15.057% with light transmission intensity of 69lux greater than conventional concrete at 28 day age. Study also focused on evaluation of Rebound Hammer test results for concrete incorporated with Plastic Optical Fiber. Moreover, the stress-strain relationship showing actual behaviour of fiber concrete under compression is highlight in study. Based on the results it is concluded that the presence of plastic optical fiber in concrete material does not impair its mechanical properties and it represents a new way to harness the sun's energy because of its excellent light transmission capacity. [ABSTRACT FROM AUTHOR]

• Notch POF integrated with smartphone as the sensor. • Notch POF sensors for liquid level and refractive index monitoring are explored. • The two types of POF sensors are compared for liquid level and refractive index monitoring. • The sensors present here are promising prospects for industrial or agricultural monitoring. Smartphone-integrated notch POF sensors with two different types (U-shaped and spiral) are demonstrated in this paper for liquid level and RI monitoring. The level and RI changes are measured by the loss of light intensity due to the notch on the POF fabricated from 3D-printed cut molds. The effects of different notch depths for two sensor types are explored. The highest sensitivity of the sensors we presented here can reach 0.59 %/cm in U-shaped type in level monitoring and 107.6 ± 4.4 %/RIU in U-shaped type in RI monitoring. The two sensor types respond differently to the notch depth, resulting in their different range of applications. Taking advantage of easy fabrication, low-cost and equipment requirements, customizable with two types, portability, and convenient real-time analysis, the sensors have promising prospects for industrial or agricultural monitoring. [ABSTRACT FROM AUTHOR]

• An intelligent wearable plastic optical fiber (POF) integrated sensor system. • Video image sampling greatly improves system integration and sampling frequency. • Radial basis function neural network (RBF-NN) accurately recognizes human motion patterns. In recent years, the development of flexible bend sensors and their detection devices has attracted great interest. In this paper, an intelligent wearable plastic optical fiber (POF) integrated sensing system for human motion detection is presented. The system consists of POF bend sensors and a wearable fiber bend detection meter (WFBDM). By capturing the POF array image from the video stream, it realizes a sampling frequency of 91.7 times/s. It also greatly increases the integration of multiple sensors, with an integrated sensing area of only 0.35*0.35 mm2 for a single sensor. POF bending sensors with a diameter of 0.25 mm were tested using this system with a linear range of −40° to 90°, an accuracy of up to 0.4°, and a response time of 26.2 ms. The system has been successfully applied to human joint and muscle motion monitoring, and combined with machine learning to realize the intelligent recognition of human motion state. The sensing system is small in size, large in sensing range, high in sensitivity and good in stability, and has the ability of intelligent recognition and highly integrated multi-channel bend signals sensing. [ABSTRACT FROM AUTHOR]

• A POF liquid level sensor based on scattering losses with > 50 cm range and < 0.21 mm resolution is presented. • A reference probe provides stable and reliable level measurements by compensating the ambient noise and source fluctuations. • A low-cost, battery-powered and small footprint level sensor module with an LED and two photodetectors is realized. • Hysteresis was minimal for organic liquids (e.g. ethanol) and liquids at elevated temperatures, where liquid adhesion is low. The study demonstrates the development of a novel low-cost plastic optical fiber (POF) based sensor for liquid level measurement. The sensor works on the principle of reduction in scattering-based optical losses (in contrast to the increase in optical losses for evanescent wave-based sensing) in a straight decladded fiber with an increase in the liquid level due to refractive index changes in the medium surrounding the fiber. A compact optical setup is developed in-house consisting of two U-bent fiber probes coupled to a single LED on one end and two photodetectors on the other ends to measure the optical intensity changes. One of the U-bent probes is decladded over the length of the fiber to act as a test probe to measure the liquid level, while the other probe acts as a reference to compensate for the light intensity fluctuations due to light source instability and ambient conditions. The difference in voltage responses of the two photodetectors gives a measure for liquid level. We have investigated the fiber optic level sensor response to rising and falling liquid levels over 55 cm in presence of aqueous liquids of different refractive index values (1.33 to 1.38) and 95% ethanol as well as DI water at various temperatures from 16 °C up to 70 °C. A level sensitivity of 1.4 and 3.3 mV/mm for water level changes was obtained for the liquid level below and above 45 cm respectively. In addition, the fiber optic level sensor shows a stable and reproducible response over several cycles of 30 min duration at different liquid levels. The results demonstrate that this fiber optic level sensor is not only easy-to-make, cost-effective and robust but also offers sensitive, stable and reproducible instantaneous level measurements. [ABSTRACT FROM AUTHOR]

Graphical abstract A highly sensitive photocatalytic plastic optic-fiber sensor for selective detection of phenol in aqueous solutions. Highlights • A highly sensitive photocatalytic phenol optic-fiber sensor is developed. • UV-vis-light-driven photocatalytic film for detection of phenol is created. • Working principle and sensitivity of proposed sensors are theoretically analyzed. • Sensitivity, selectivity, pH immunity, and detection limit are checked. • Proposed sensor shows high sensitivity and low detection limit. Abstract We present a highly sensitive photocatalytic plastic optic-fiber (POF) sensor for the selective detection of phenol in aqueous solutions. To obtain high sensitivity and low limit of detection (LOD) of the sensor, part of the POF cladding was removed and replaced by a Canada balsam doped with GeO 2 (CBG); a UV–vis-light-driven photocatalytic material, that is a CdS-sensitized Er3+YAlO 3 /SiO 2 /TiO 2 (EYST) composite, was coated on the CBG film. To realize highly selective detection of phenol in water, a high phenol permselectivity and pH independence polymer membrane was fixed on the CdS-sensitized EYST-CBG-coated POF. Furthermore, a model was developed to show that the phenol concentration can be determined by measuring the change in transmitted light intensity of the POF sensor and the sensitivity of the sensors can be improved by employing the CdS-sensitized EYST film. The results showed that the proposed photocatalytic POF sensor has a high sensitivity of -0.39 (mg·mL−1)−1 and low LOD of 15 μg·L−1 for the selective detection of phenol in aqueous solutions with pH ranging from 2.0 to 14.0. [ABSTRACT FROM AUTHOR]

Plastic optical fibers (POFs) have many advantages compared with conventional optical fibers for sensing and monitoring applications in civil engineering. The monitoring capability of POF sensors depends on the strain transfer characteristics between POFs and host materials to a great extent. Theoretical analysis is performed to develop the strain transfer relationship between surface-bonded POFs and concrete. Besides, finite-element method is conducted for verification, and the main influencing parameters are studied respectively. The calculated results demonstrate that the effect of strain transfer is more significant when the POF is bonded close to the surface of concrete and the length of the adhesive layer ought to exceed 300 mm simultaneously, and the width, thickness, and shape of the adhesive layer have slight impact on the strain transfer. [ABSTRACT FROM AUTHOR]

This paper presents a novel respiration sensor based on multiple in‐fiber microholes drilled along a plastic optical fiber (POF) that is stitched to a waist‐band wrapped around the patient's abdomen. The bending loss of a POF with a single microhole is analyzed in order to enhance the sensor sensitivity. Several sensors were fabricated using a 1.5 mm‐diameter POF with different numbers and spacing of 0.7 mm‐diameter microholes. The sensitivity of the respiration sensor increased when increasing the number and spacing of the microholes, where the POF respiration sensor with seven 0.7 mm‐diameter in‐fiber microholes spaced at 15 mm showed the highest sensitivity and sufficient strength for respiratory monitoring. Thus, the experimental results confirmed that a POF sensor based on in‐fiber microholes can be effectively used to monitor the respiration of patients. [ABSTRACT FROM AUTHOR]

In recent years, the technology of multi-mode fiber (MMF) output speckle recognition has been widely used in the fields of optical imaging, endoscope devices, and fiber optic sensor. However, previous studies focused on the single-input transmission mode on a single fiber, which limited the application range of MMF. Meanwhile, the fiber optic sensors based on speckle recognition often lack multiplexing ability. In this paper, multiple lateral sections of plastic optical fiber (POF) are polished, and the images corresponding to 26 letters are coupled into POF form them. When images couple into POF from one lateral polishing section, by analyzing the output speckles based on deep learning technology, the accuracy of speckles recognition with convolution neural network (CNN) reaches over 95% and the structural similarity (SSIM) of reconstructed speckles with U-Net reaches up to 0.96. When two images couple into POF from different lateral polishing sections simultaneously, the output speckle can be reconstructed to the two images respectively, and the average SSIM value for them is 0.95. The experiment proves that the images coupled into fiber through the lateral polishing section of POF can be recognized and reconstructed well by output speckle analysis. This technology can promote the multiplexing ability of the speckles-recognition based fiber sensors or be applied to the field of fiber endoscopes. • A method to improve the multipoint sensing ability and multi-parameter sensing ability for fiber sensor based on specklegrams. • Two simultaneous input image can be reconstructed and reconstructed by one output specklegram. • A new image transmission structure based on deep learning technology. [ABSTRACT FROM AUTHOR]

• A RI sensor was researched on eliminating the influence of ambient temperature. • A F-P interferometer based on PVC film is used to demodulate temperature shift. • The accuracy of the sensor is high and it has good repeatability. An optical fiber sensor based on a gradually hot-pressed flatted plastic optical fiber (POF) and F-P interference structure is proposed to eliminate the effect of ambient temperature drift in the refractive index (RI) detection of glucose concentration. Based on the analysis of the influence of the sensor itself and the RI change of solution on the transmitted light intensity under the effect of temperature, a self-calibration formula was established by means of the peak wavelength and the transmitted light intensity of interference peak were used as information carriers to calibrate the parameters. The results of the validation show that the temperature drift compensation method proposed in this paper is feasible. The maximum relative error between the measured RI after compensation and actual value is only 0.032%, and it has good repeatability. The precision to the RI with temperature compensation of the gradually hot-pressed flatted POF and F-P interference structure has potential applications in the biochemistry, medical diagnosis, and environmental monitoring. [ABSTRACT FROM AUTHOR]

Highlights • Low cost solar tracker w/ stepper motor, Fresnel lens, plastic optical fiber bundle. • Tracker guides solar light to ambience to reduce power consumption for lighting. • The new photobioreactor costs less than conventional window-photobioreactor. • We demonstrated a higher efficiency in illumination and cultivation. Abstract Although within the group of countries with the highest solar irradiation index in the world, Brazil still underuses its natural power. Brazil's hydropower energy today makes up 68,5% of the total energy produced, in contrast however, photovoltaic energy production is still only 0.01%. As an effort to open up new frontiers for solar energy uses, the main objective of this project was to use solar energy in form of light to reduce the power consumption required for continuously lighting any kind of environment as well as to propose a new technology for illuminating a conventional window-type photobioreactor (PBR) in the cultivation of microalgae for biofuel production in order to reduce their associated costs. The system is composed by a solar tracker, an electromechanical control, a Fresnel lens and a plastic optical fiber (POF) bundle, in which tip the lens concentrates the solar radiation. Therefore, at the other end of the bundle, the POFs can be distributed homogeneously in any local where one wants to illuminate. The solar tracker is able to track the Sun from sunrise to sunset using an algorithm whose function is to calculate the Sun position according to the local time and latitude using an equatorial mount structure. In addition, some sensors are employed for monitoring relevant parameters, for instance, the light intensity inside the POF bundle, the right ascension and declination angles of the tracker and the solar radiation. These parameters can be downloaded in real time through a specially designed mobile application. As application of the solar tracker, two projects were developed and described in this paper: two kinds of solar luminaires for illumination of internal ambiences and a closed photobioreactor by POF illumination, with nontransparent material, free of outside contamination with low cost and the study of the produced biomass through the lipid content. Both applications were compared in performance with their conventional counterparts and, as a conclusion, it is shown that in both cases they can substitute their conventional counterparts with advantages. [ABSTRACT FROM AUTHOR]

Evanescent wave‐based excitation of noble metal nanostructures on fiber core surface allows simultaneous excitation over a larger area in comparison with free space coupling, and hence highly suitable for development of surface‐enhanced Raman scattering (SERS)‐based sensor applications. This study describes the development of plasmonically active U‐bent plastic optical fiber (POF) probes for SERS‐based sensing. The SERS activity of gold nanostructures on the fiber probe surface obtained by means of electroless deposition, sputtering, and chemisorption of nanoparticles are thoroughly characterized using a confocal microscopic setup. Influence of excitation wavelength and laser excitation power on SERS activity and stability of the plasmonic U‐bent probes is evaluated. Gold‐sputtered POF probes and gold nanoparticle immobilized POF probes show higher enhancement factor in the order to ~108. A biosensor application of these POF‐based SERS sensors is demonstrated by realizing a sandwich immunoassay with 4‐MBA as Raman label. This study describes development of plasmonically active U‐bent plastic optical fiber probes for SERS‐based sensing. The SERS activity of gold nanostructures on the probe surface obtained by means of electroless deposition, sputtering, and chemisorption of nanoparticles are characterized using a confocal microscopic setup. Gold‐sputtered probes and gold nanoparticle immobilized probes show higher enhancement factor in the order to ~108. These probes are demonstrated for biosensor application as SERS sensors by realizing a sandwich immunoassay with 4‐MBA as Raman label. [ABSTRACT FROM AUTHOR]

Sulfate-reducing bacteria (SRB) are considered one of the oldest forms of microorganism that date back about 3.5 billion years and are common in anaerobic environments such as oil wells. SRB, in their metabolic process, produce hydrogen sulfide that contaminates the oil and is extremely toxic to humans, besides being one of the main causes of corrosion in the pipes. This paper presents a fast response-time biosensor, made of 1-mm diameter plastic optical fiber (POF) to detect SRB in production water. The physical principle for the operation is the interaction of the measurand with a curved waveguide based on the changes of the refractive index of the medium. The POF probes were functionalized with antibody anti-SRB and tested with Desulfovibrio alaskensis concentrations of 10 4 , 10 6 and 10 8  MPN/mL (most probably number per mL). The optoelectronic setup consists of an 880 nm LED connected to a U-shaped probe. The system responded in about 30 min for concentrations of 10 4 , 10 6 and 10 8  MPN/mL, encouraging an optimization of the sensitivity to read concentration of 10 3  MPN/mL or smaller. To the best of our knowledge, this is the first sensor to date capable to detect SRB with such small-time response. [ABSTRACT FROM AUTHOR]