Polyaniline coated on tapered multimode fiber for ammonia sensing

This paper presents optical response of polyaniline coated on tapered multimode fiber towards ammonia gas. Polyaniline was deposited onto tapered multimode fiber by spray-coating method. Surface morphology of the coating was observed under scanning electron microscope. Absorbance measurement was done using spectrometer while the coated fiber was exposed to ammonia gas with concentration varies from 0.125% to 1% at room temperature. The absorbance is proportional to the ammonia concentration. The response and recovery time is 2.27 minutes and 10 minutes, respectively

Fabrication and development of flat fibers

This paper reports the parameters that affect the fabrication of Flat Fibers, including preform size and doping, furnace temperature, preform feed speed, fiber drawing speed, fiber dimension, fiber quality and shape, vacuum pressure and core dimension. The feed and draw speed generally follows the simplified mass conservation law to draw the fiber to a specific dimension. The preform wall thickness affects the vacuum pressure and furnace temperature that is needed to 'flatten' the fiber. The preform wall thickness is directly proportional to the volume of glass inside the neck-down region. The wall thickness of the preform and its dopant will also affect the size of the cladding and core dimension. Finally, some issues associated with the fabrication of Flat Fibers are also observed and discussed, including fabrication of Flat Fibers with non-uniform dimensions, deformed shapes, unwanted airholes and poor quality of the Flat Fibers

Joint Adaptive Beamforming And Adaptive Modulation Techniques For Wireless Communication Systems

The study begins by investigating the potential benefit of utilizing adaptive modulation mode selector at the output of adaptive beamformer. By applying this combination approach, the adaptive modulator is designed to assist the adaptive beamformer in determining the need to recalculate the adaptive beam forming weight vector. The novelty of this approach lies in the ability of the joint technique to reduce the weight recalculation rate, thus saving the processing power. Computer simulation was carried out to compare the performance of the proposed joint adaptive beamforming adaptive modulation (ABF-AM) with the conventional adaptive beamforming fixed modulation (ABF-FM) for the case of one and two interferes. Results for both cases show that the proposed ABF-AM is able to fulfil the target bit error rate (BER) of 10, while improving performance by reducing the required average received signal-to-interference-plus-noise ratio (SINR) as compared to the AB F-FM technique

Room temperature ammonia sensing using tapered multimode fiber coated with polyaniline nanofibers

We demonstrate an ammonia sensor composed of a tapered multimode fiber coated with polyaniline nanofibers that operates at room temperature (26°C). The optical properties of the polyaniline layer changes when it is exposed to ammonia, leading to a change in the absorption of evanescent field. The fiber sensor was tested by exposing it to ammonia at different concentrations and the absorbance is measured using a spectrophotometer system. Measured response and recovery times are about 2.27 minutes and 9.73 minutes, respectively. The sensor sensitivity can be controlled by adjusting the tapered fiber diameter and the highest sensitivity is achieved when the diameter is reduced to 20 µm

Feasibility studies of polyaniline nanostructures coated on tapered optical fiber for ammonia sensing

Polyaniline (PANI) has been used for ammonia (NH3) sensing for several decades, mostly in electrical based sensors due to its variation in conductivity during the interaction. Optical sensors are known to have advantages in certain aspects as compared to electrical sensors, but this area of research has not been fully explored. Therefore, this research project aims to explore optical based NH3 sensor with the incorporation of PANI nanostructure. Tapered multimode fiber (MMF) was chosen as the transducing platform for the sensor because of ease in fabrication, high sensitivity and its suitability for remote sensing applications. The sensitivity of tapered fiber based sensors can be improved by reducing the waist diameter. The influence of PANI nanostructure morphology, thickness and dopants on the sensing performance was also studied in this thesis. In this project, PANI nanostructures were synthesized and deposited on tapered MMF using two methods. The first method was in-situ deposition method, where poly(methyl vinyl ether-alt-maleic acid)(PMVEA)-doped PANI (PANI-PMVEA) nanogranules and nanofibers were grown on tapered MMF surface during polymerization process. For the second method, camphorsulfonic acid (CSA)-doped PANI (PANI-CSA) nanofibers were spray coated on the tapered MMF. Three processes were involved in the preparation of PANI-CSA, namely the synthesis of hydrochloric acid-doped PANI (PANI-HCl), the dedoping of PANI-HCl to obtain emeraldine base PANI (PANI-EB) powder and the redoping of PANI-EB with CSA to obtain PANI-CSA nanostructures. The thickness and morphology of PANI nanostructures were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The formation of PANI nanostructures in emeraldine salt form was confirmed from molecular vibrational analysis using Raman Spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). The response of the sensors towards NH3 at different concentration was measured using cumulative absorbance change within the wavelength range of 500 – 800 nm. The sensing performance was evaluated in terms of response time, recovery time, sensitivity and repeatability. PANI-PMVEA coating thickness and morphology was varied by varying the deposition duration and PMVEA/aniline ratio. The highest sensitivity was achieved by the most uniformly-distributed nanogranules PANI-PMVEA coating with thickness of approximately 913 nm. The achieved sensitivity, response and recovery time was 2.19/vol%, 2.82 minutes and 11.52 minutes, respectively. PANI-CSA nanofibers were coated on tapered MMF with different waist diameters. The highest sensitivity of 2.44/vol% was attained by the smallest diameter (20 μm) sensor with PANI-CSA coating of approximately 700 – 850 nm. The response and recovery time are 1.73 minutes and 12 minutes, respectively. The sensor using PANI-CSA nanofibers have higher sensitivity and faster response than the sensor using PANI-PMVEA nanostructures at 1% NH3

Sensitivity improvement in a fiber macrobending refractive index sensor

In this paper, sensitivity improvement in a fiber macrobending refractive index sensor is studied and an improved sensor model is proposed. The sensitivity can be improved by increasing the evanescent field produced by the fiber when it is bent. Theoretically, an increase in bending loss will increase the evanescent field region. The parameters that affect the bending loss are bending radius of the fiber, number of wrapping turns and critical radius of curvature (Rc). From the theoretical analysis results, a refractive index sensor with improved sensitivity is designed by using values from the analysis as a guideline: bending radius = 5.5 mm, number of wrapping turns = 1 - 5 turns and Rc = 5 - 13 mm. The proposed sensor uses a single mode fiber with an NA of 0.2 where the fiber has a bending radius limit of 5 mm. The cladding at the sensing part of the fiber is removed and the sensor probe is U-shape with several numbers of turns. The proposed sensor is expected to provide high sensitivity with a simple sensor configuration

Numerical analysis of metal-layer in optical fiber clad

This paper presents a simulation result of confinement loss in a specialty optical fiber. The optical fiber is designed to have a thin metal-layer in the optical fiber clad. The optimum distance of copper layer from fiber core is determined by calculating the confinement loss. The confinement losses are observed by varying the copper diameter from core. The COMSOL multi-physics 5.3 is used as the simulation tool. The proposed design may potentially pave a broad range of applications including high-sensitive plasmonic biosensor and filtering devices

Non-Uniformity of Non-Thermal Plasma Formation: Using FBG as Temperature Sensors

This research investigates fiber Bragg grating (FBG) temperature sensing performance in monitoring non—uniformity of non-thermal plasma (NTP) formation in a packed-bed reactor using FBG operating at atmospheric pressure. Two FBGs made from germanium doped fiber were embedded inside and outside the PBNTP reactor to allow for comparison between the temperatures inside and outside of the reactor to be made. Each FBG comes with three grating series, which allow the reactor temperatures at three different locations inside or outside the reactor to be measured and compared. Two types of plasma, namely nitrogen (N2) and argon (Ar) were generated in the reactor at a gas flow rate in the range of 2 - 7 L/min and applied voltage in the range of l - 20 kV. It was found that the PBNTP reactor temperature varies up to 20 oC at different positions inside and up to 40 oC outside of the reactor. This finding shows the non-uniformity of plasma formation and the nature of the plasma's localized thermodynamic equilibrium (LTE). The sensitivity of the FBG temperature sensor used in this study is estimated at 10.36 - 10.50 pm/oC

IoT-based Temperature and Humidity Real Time Monitoring System for Beekeeping using LoRa Technology

In stingless beekeeping, monitoring the temperature and humidity in the beehive is crucial to increase the honey yield and ensure the survival of the bee colony. However, the conventional method of checking the beehive is laborious and time consuming. This paper proposes an IoT based real time remote monitoring system that enables the beekeeper to monitor the temperature and humidity in the beehive remotely through mobile application and web dashboard. The system uses low-power wide-area network (LPWAN) technology, long-range (LoRa) to transmit the data from the sensor node which implements DHT 22 sensor at the beehive to the cloud via a LoRa gateway

Smart and Intelligent Prayer System for Elderly Muslim with IoT

An assistive and monitoring prayer system has been designed to help elderly Muslims in performing their daily prayers. However, the system has several limitations in the aspect of efficiency, cost, size, complexity, security and usability. In this paper, several enhancements have been proposed to improve the existing smart prayer system including a better approach to retrieve exact prayer times, efficient way to retrieve current date/time, two different sensors used to detect the physical movements, smaller microcontroller with a built-in Wi-Fi module and the fabrication of PCB board. On the monitoring system, this project offers a more user’s friendly mobile application with several enhanced features. Reminder and authentication features are added to the mobile application for increased security and usability. The mobile application only allowed authorized or registered users to use the mobile application to view prayer performance of the elderly and send a prayer reminder to the elderly. The proposed system implements Internet of Things (IoT) technology, with a microcontroller communicating with the database through Wi-Fi, and data is modified before being displayed via the mobile application. Experimental testing shows a high level of support for the system's commercialization due to its ability to assist and monitor the elderly with their daily prayers. This new smart prayer system offers a more reliable assistive and monitoring system for elderly Muslim