This study proposes an optical fiber sensor with a single mode - no-core - single mode (SNS) structure. The sensor employs zinc oxide (ZnO) as a sensing layer coated over the no-core fiber (NCF) region. ZnO is introduced to absorb volatile organic compound (VOC) biomarkers of diabetes, utilizing an evanescent sensing mechanism. The ZnO colloidal solution used for this purpose was synthesized through aqueous chemical growth. A cost-effective airbrush was used for coating a thin layer of ZnO over the NCF. Several material characterizations, including FE-SEM, UV-Vis, and XRD, were conducted to validate the presence of the ZnO layer over the NCF. The study investigates VOC biomarkers for diabetes, such as acetone, isopropanol, and ethanol, with 100-500 ppm concentrations. These VOCs were chosen because they belong to the same class of alcohol found in the exhaled breath of individuals with diabetes. Notably, the optical fiber sensor exhibited the highest sensitivity to acetone, with a sensitivity of 0.0028 nm/ppm. In addition, the sensor demonstrated selectivity to acetone, highlighting the significant role played by the morphology of the ZnO layer. The results presented in this study suggest that the proposed sensor has the potential for real-time and non-invasive monitoring of acetone vapor, a biomarker in exhaled breath for diabetes. Its advantages include cost-effectiveness and simple fabrication processes, making it a promising tool for diabetes management and diagnosis.
A numerical modelling to theoretically investigate and analyse the characteristic of the surface functionalised optical fibre based sensor to detect volatile organic compounds (VOCs) biomarker is introduced in this paper. A 125-micron diameter of coreless silica fibre (CSF) connected to single-mode fibre (SMF) at both ends to achieve a structure of SMF-CSF-SMG is proposed to detect VOCs biomarkers for diabetes such as acetone and isopropanol. The coreless fibre region is considered to be a sensing region where the multimode interference (MMI) occurs having a higher light interaction at the interface between the fibre and sensing medium which leads to the enhancement of sensitivity. The sensing region undergoes surface functionalisation with Au-silane for the sensor to be selectively detect VOCs biomarker with electrostatic absorption. The length of the sensing region is numerically optimised to achieve a reimaging distance where the highest possible of coupling efficiency occurs and the maximum output signal can be obtained. Coupling efficiency spectra at different volume fractions of gold nanoparticles with various acetone and isopropanol concentrations are also presented. A sensitivity of the Au-silane functionalised optical fibre sensor is achieved by using the analysis of wavelength shift interrogation. The results show the spectra undergoes red-shift phenomenon in the near-infrared region (NIR) when concentrations of acetone and isopropanol are increased. The functionalisation of Au-silane on the optical fibre sensor provides a higher sensitivity compared to the unfunctionalised sensor as it shows more dramatic shifts of absorption spectra when there is a change in VOCs biomarker concentration.
An optical fiber sensor based on Fabry-Pérot interferometer to measure the refractive index changes due to oxygenation level changes in hypoxic tumors for radiotherapy treatments is proposed. The sensors have an outer diameter of 220μm with a 20-30μm length air-cavity and a 30μm thickness end cap located at the tip of the sensor. The sensors are used to measure the phase change in the received optical spectrum when there is a change in refractive index using a Fast Fourier Transform based analysis method. The refractive index change is measured in order to determine the oxygenation level in hypoxic tumors. In this paper, different concentrations of iso-propanol solution are prepared to produce refractive index values between 1.3438 and 1.3655 in order to mimic the refractive index of hemoglobin. The sensors are coated with a 100 nm thick gold layer and a comparison is made with non-coated sensors. The coated sensors have a resolution in order of 10-3 RIU.
In this paper, an ormocomp polymer nanowire with possible use in integrated-optics sensing applications is presented. We discuss the structure design, the fabrication process and present results of the simulation and characterization of the optical field profile. Since the nanowires are designed and intended to be used as integrated optics devices, they are attached to tapered and feed waveguides at their ends. The fabrication process in this work is based mainly on the nanoimprint technique. The method assumes a silicon nanowire as an original pattern, and polydimethylsiloxane (PDMS) as thesoft mold. The PDMS mold is directly imprinted on the ormocomp layer and then cured by UV light to form the polymer based nanowire. The ormocomp nanowires are fabricated to have various dimensions of width and length at a fixed 500nm thickness. The length of the nanowires is varied from 250 µm to 2 mm, whereas the width of the structures is varied between 500nm and 1µm. The possible optical mode field profile that occurs in the proposed polymer nanowire design is studied using the H-field finite element method (FEM). In the characterization part, the optical field profile and the intensity at the device output are the main focus of this paper. The various lengths of the nanowires show different characteristics in term of output intensity. An image processing is used to process the image to obtain the intensity of the output signal. A comparison of the optical field and output intensity for each polymer nanowire is also discussed.
Today there is an increasing surge in Surface Plasmon based research and recent studies have shown that a wide range of plasmon-based optical elements and techniques have led to the development of a variety of active switches, passive waveguides, biosensors, lithography masks, to name just a few. The Terahertz (THz) frequency region of the electromagnetic spectrum is located between the traditional microwave spectrum and the optical frequencies, and offers a significant scientific and technological potential in many fields, such as in sensing, in imaging and in spectroscopy. Waveguiding in this intermediate spectral region is a major challenge. Amongst the various THz waveguides suggested, the metal-clad waveguides supporting surface plasmon modes waves and specifically hollow core structures, coated with insulating material are showing the greatest promise as low-loss waveguides for their use in active components and as well as passive waveguides. The H-field finite element method (FEM) based full-vector formulation is used to study the vectorial modal field properties and the complex propagation characteristics of Surface Plasmon modes of a hollow-core dielectric coated rectangular waveguide structure. Additionally, the finite difference time domain (FDTD) method is used to estimate the dispersion parameters and the propagation loss of the rectangular waveguide.
KEYWORDS: Receivers, Light emitting diodes, Analog electronics, Transmitters, Signal to noise ratio, Sensors, Multiplexing, Radio optics, Polarization, Telecommunications
From the past until now, a radio frequency technology takes an important role in a communication system. Optical
wireless technology is gaining more importance and becoming a smart alternative in the communication systems
since noise and interference problem issues can be minimized. This project aims to create a smart environment by
using optical wireless technology with a color multiplexing scheme. RGB Light Emitting Diodes (RGB-LEDs) are
used as a visible white light source as they are becoming the next generation of lamps. A color de-multiplexing
scheme is applied at the receiver port.
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