Jurnal OptoElektronik

Data Fusion K-Means Clustering for Seismic Signal Classification Using Integrated DAS-Geophone Sensing

Long Muhammad Haziq Long Hassan — 2025-11-02

Distributed Acoustic Sensing (DAS) and geophone technologies are implemented for seismic monitoring with a limited comparative analysis between these systems particularly in integrating data from heterogeneous sensors. One of raising inutilization of advanced machine learning for seismic data classification. Data fusion is promising solution, which capable of combining information from multiple sources to improve accuracy and robustness of seismic interpretation. Hence, in this study focus on integrating DAS and geophone data using data fusion by utilizing unsupervised machine learning with K-Means clustering to classify seismic signals. Seven clusters are used in this study which used PCA and t-SNE scatter plot for the K-Mean clustering, Results show that the proposed methodology demonstrates effectiveness in distinguishing between common and anomalous seismic events. Visualization and cluster analysis confirm the interpretability and practical value of this framework. From the findings, this study offers promising basis for anomaly detection and routine monitoring system with future works aimed at improving clustering techniques.

Relative Humidity Sensor using Tungsten Disulfide Coated on Tapered Microfiber

Naimah Mat Isa — 2025-10-30

A two-dimensional transition-metal dichalcogenide material like tungsten disulfide (WS₂) can be used to increase the sensitivity of a few sensing applications. The impact of WS₂ coating on tapered region microfiber (MF) for relative humidity (RH) sensing applications was examined in this work. The typical single-mode fiber (SMF) and waist diameter diameters of Microfiber 3 µm were tapered, using the flame brushing technique. The drop-casting process, a simple deposition technique, was then used to coat the microfiber in WS₂. Depositing WS₂ onto the tapered zone resulted in high humidity sensor sensitivity because the MF had a strong evanescent field that enabled quick near-field interaction between the directed light and the environment. To demonstrate repeatability and sensor stability, the experiments were repeated three times to quantify the average transmitted power. Different %RH concentration was evaluated with the MF sample size. Additionally, at room temperature and in the %RH range of 40% to 60% RH, the performances of coated and uncoated microfiber were examined. Thus, microfiber coated with WS₂ encourages enhancement in the evanescent field effect in optical fiber humidity sensor.

Label-free SERS-Based Aptasensor for SARS-CoV-2 S-Proteins Detection

Fariza Hanim Suhailin — 2025-11-05

This study presents a label-free surface-enhanced Raman spectroscopy (SERS) aptasensor for the sensitive and selective detection of SARS-CoV-2 spike (S-) proteins of Wuhan and Omicron variants. Gold nanoparticles (Au NPs) were deposited onto hydroxylated silicon (Si) substrates and functionalized with variant-specific aptamers. The SERS aptasensor demonstrated a strong, concentration-dependent Raman response from 1 nM to 20 µM, with a sensitive and prominent peak at 1590 cm⁻¹ attributed to Au–thiolate bonding. The Omicron variant produced significantly higher SERS intensity than the Wuhan variant, suggesting enhanced aptamer binding affinity and Raman responses. Beside high sensitivity and capability for variant discrimination, a strong linear correlation between SERS intensity and protein concentration supports the potential of label-free SERS aptasensor for quantitative diagnostics of COVID-19.

Succinyl-NCQD Enhanced LSPR for Chlorine Detection in Lipid Matrices

Qayyum Othman — 2025-10-30

Chlorine contamination in crude palm oil (CPO) is a key factor in the formation of 3-monochloropropane-1,2-diol (3-MCPD), a harmful contaminant with carcinogenic potential. Existing detection methods such as ion chromatography (IC) and total chlorine analyzers (TCA) are accurate but complex, time-consuming, and not suitable for rapid or on-site testing. This study was conducted to develop a localized surface plasmon resonance (LSPR) optical sensor for detecting organic chlorine in edible oil matrices. The main objectives of this study are to investigate LSPR sensing for chlorine detection, fabricate a composite-based LSPR sensor using succinyl-functionalized nanocarbon quantum dots (succinyl-NCQD) and silver nanotriangles (AgNT), and evaluate its sensitivity in detecting low chlorine concentrations. Succinyl-NCQD was chosen as the sensing material to improve binding interaction and signal response. The sensor showed a strong linear response in the 0.5–5 ppm range with a sensitivity of 1.6877 nm ppm⁻¹, a limit of detection (LOD) of 0.56 ppm, and a limit of quantification (LOQ) of 1.85 ppm.

Enhancing Bandwidth and Efficiency in GaN LEDs for VLC Systems

Norhanis Aida Mohd Nor — 2025-11-02

Gallium nitride (GaN) light-emitting diodes (LEDs) are essential for visible light communication (VLC), enabling high-speed data transmission and energy-efficient lighting. However, c-plane GaN LEDs face limitations due to polarization fields and the quantum-confined Stark effect (QCSE), restricting bandwidth and data rates. Advances in semi-polar and non-polar GaN structures have enhanced bandwidth, supporting gigabit-per-second VLC performance. Optimizing the active region through quantum well thinning and hybrid quantum dot integration further boosts modulation speeds. Additionally, Europium (Eu³⁺) doping provides high-color-purity red emission and faster recombination, improving bandwidth and reducing efficiency droop. This review highlights these innovations for high-speed VLC systems.

A Robust Brillouin Frequency Shift Extraction in BOTDR under Noisy condition Using AdaBoost Regression

Intan Fatimah Sasila Ghadzali — 2025-11-05

Accurate extraction of the Brillouin Frequency Shift (BFS) is vital for high-performance distributed fiber sensing, particularly under noisy or low-resolution conditions. This study presents a robust machine learning approach using the AdaBoost regression algorithm to extract BFS from Brillouin Gain Spectra (BGS) under challenging spectral scenarios, including low signal-to-noise ratio (SNR), limited frequency range, and coarse resolution. Experimental BGS data were obtained from a Differential-Cross Spectrum (DCS) BOTDR setup based on the correlation of two optical pulses, measured over a temperature range of 25°C to 70°C. To enhance model generalization, synthetic noisy datasets were generated through data augmentation, and Savitzky-Golay filtering was applied to preserve spectral peak structure. The results demonstrate the model’s robustness and highlight the importance of maintaining high SNR, sufficient frequency coverage, and fine resolution for reliable BFS extraction in practical sensing environments.

Polarisation Control of Tapered Optical Fiber for Selective Whispering Gallery Mode Resonance Excitation

Mohd Narizee Mohd Nasir — 2025-10-30

Tapered optical fiber evanescent light wave polarization control is demonstrated with the utilization of free-space optics polarization resolved set-up. TE- and TM-polarised lasing light discrimination of > 20 dB could be achieved with the proposed setup and with tapered optical fiber of 2 μm waist diameter. Investigation on the performance of the proposed tapered optical fiber with whispering gallery mode (WGM) optical microresonators show distinguishable TE and TM group-mode families with high Q-factor and sharp wavelength dip contrast.

Recent Advances in 2D Photonic Materials: A Review of Optical Properties and Integration Challenges

Woan Wen Tan — 2025-11-05

Two-dimensional (2D) materials are emerging in photonics due to their atomic-scale thick nature, strong interaction with light, and diverse electronic characteristics. This review explores the use of 2D materials like graphene, TMDs, BP, and hBN, focusing on their roles in high-speed modulation, photodetectors, and creating flexible, adjustable light sources. We compare their optical properties and examine their suitability for advanced photonic technologies. Material synthesis, such as wafer-scale growth and van der Waals stacking, have significantly improved their compatibility with integrated photonic platforms. However, there are critical challenges that need to deal with, such scalability, environmental stability, CMOS compatibility. Material encapsulation techniques, producing large-area growth methods, and interface engineering are being actively pursued to overcome these limitations. This review summarizes current progress and ongoing challenges in the field.

Optimizing Nutrient Detection in Hydroponic Solutions through UV-Vis-NIR Spectroscopy and Machine Learning Modelling

Rozita Sulaiman — 2025-11-02

Accurate nutrient determination is crucial for optimizing hydroponic systems. Traditional methods like electrical conductivity (EC), ion-selective electrodes (ISE), and colourimetry are hindered by limited ion specificity, high maintenance, and prolonged analysis times. Current spectroscopy-based AI methods also require extensive sample sizes, complicating real-time use. This study presents a rapid UV-Vis-NIR spectroscopy technique integrated with machine learning (ML) for predicting nitrogen and phosphorus levels using minimal samples. Among five regression models tested Support Vector Machine Regression (SVR), Linear Regression (LR), Partial Least Squares Regression (PLSR), Random Forest Regression (RFR), and Gradient Boosting Trees Regression (GBTR) linear regression (LR) excelled for nitrogen prediction (R²=0.9734; RMSE=19.2345 ppm), although its performance slightly dropped during external validation (R²=0.923; RMSE=30.6666 ppm). Random forest regression (RFR) showed superior accuracy for phosphorus prediction (R²=0.9578, 0.9468). Integration of SVM classification with LR and RFR further improved accuracy (R²=0.96) despite 26 samples. This ML-based spectroscopy model enables rapid, precise nutrient monitoring, enhancing crop yield and sustainability in hydroponics.

Performance Comparison of Thiophene Derivative Films for SPR-Based Creatinine Detection

Nur Afifah Ahmad Nazri — 2025-10-30

This study presents a comparative SPR analysis of tetrahydrothiophene (THT) and benzo[b]thiophene-2-carboxaldehyde (BTCA) as sensing layers for creatinine detection. Using an SPR setup, both materials exhibited concentration-dependent spectral shifts. The BTCA-based sensor demonstrated higher sensitivity (3.3557 nm/(mg/dL)), better linearity (R² = 0.9636), and lower detection limits than THT, attributed to stronger molecular interactions, including hydrogen bonding and dipole-dipole effects. These results confirm BTCA's superior plasmonic response, supporting its potential as a label-free sensing material for creatinine detection in clinical diagnostics.

Comparison of Filtered and Direct RGB LED Illumination in Confocal Imaging for Cellular Imaging

Muhammad Faizul Hadi Abu Kasim — 2025-11-02

This study investigates the comparative performance of filtered and direct RGB LED illumination in confocal microscopy for biological imaging. Rotifera whole-mount samples were imaged under both illumination modes, and image quality was assessed using signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) metrics. The highest SNR was recorded under filtered green LED illumination, whereas the highest CNR was achieved with direct red LED light. These results indicate that filtered RGB illumination enhances overall image uniformity, while direct RGB lighting more effectively accentuates structural contrast, depending on the specific imaging objective.

Single Mode Fiber-Based SPR Sensor for Enhanced Detection of Air Contaminants

Marinah Othman — 2025-12-01

This paper investigates the optical characteristics of a single mode fiber (SMF) based surface plasmon resonance (SPR) sensor. Utilizing the finite element method (FEM) in COMSOL, a numerical model of the SMF-based sensor is developed and its performance evaluated based on varying gold thicknesses (30 nm, 40 nm, and 50 nm). Results show that thinner coatings lead to deeper evanescent wave penetration and higher field intensity at the sensing interface for air contaminant monitoring applications.

Water Contact Angle Optimization for K-SPR Biosensing Application

Nur Akmar Jamil — 2025-11-04

Surface wettability, measured via water contact angle (WCA) assessments, is an essential parameter in evaluating sensor surfaces' characteristics in plasmonic biosensing, particularly in Kretschmann-based surface plasmon resonance (K-SPR). This study examines the influence of heptylamine plasma polymerization parameters on WCA measurement and correlates these surface alterations with the sensitivity of K-SPR biosensors. The correlation between plasma deposition power and WCA was measured using ImageJ software, and SPR angular spectra were evaluated to determine the refractive index sensitivity. The results demonstrate that optimizing plasma deposition conditions provides good linearity in terms of plasmonic biosensing.

Surface Plasmon Resonance Polymer Optical Fiber Sensor for Enhanced Oxygen Detection with PdTFPP-Based

Azween Hadiera Hishamuddin — 2025-11-02

This study presents an enhanced oxygen detection method combining fluorescence sensing with surface plasmon resonance (SPR) using a multimode polymer optical fiber (POF). The POF is coated with a silver layer for SPR and the palladium-based dye PdTFPP, known for its high oxygen sensitivity. PdTFPP alone showed an emission peak at 668.62 nm, with intensity decreasing as oxygen concentration increased. The SPR-enhanced sensor showed a sensitivity of 0.1045 compared to 0.0944 for PdTFPP alone, demonstrating improved performance.

Passively Q-switched erbium-doped fiber laser based on Polyaniline Boron Nitride as saturable absorber

Hasanain Naser — 2025-10-30

This study explores the experimental implementation of Polyaniline Boron Nitride (PANI-BN) as a saturable absorber (SA) to generate Q-switched pulses within a 1.5 μm erbium-doped fiber laser (EDFL) cavity. The research demonstrates successful and stable Q-switched operation by optimizing the loss and gain parameters within the laser cavity. The system operated with pump powers ranging from 92.7 mW to 212.1 mW, during which the repetition rate increased from 72.27 kHz to 93.9 kHz. Simultaneously, the pulse width decreased from 6.65 μs to 5.1 μs, highlighting the controlled dynamics of the system. The Q-switched EDFL system emitted at a central wavelength of 1530.2 nm, delivering peak pulse energies that ranged from 9.7 nJ to 976 nJ, and achieved a slope efficiency of 5.5% and a signal-to-noise ratio (SNR) of 57.6 dB. These results underscore the promising potential of PANI-BN as an efficient saturable absorber, offering significant advantages for enhancing the Q-switching performance in fiber laser cavities. This innovation opens the door for the development of more efficient, reliable fiber laser systems with wide-ranging applications in telecommunications, industrial, and scientific fields.

Tunable Wide Dissipative Soliton Resonance Generation by Figure-of-Eight Nonlinear Amplifying Loop Mirror

Zuraidah Zan — 2025-12-01

We demonstrate dissipative soliton resonance (DSR) mode-locking using a nonlinear amplifying loop mirror (NALM) in a C-band erbium-doped fiber (EDF) laser. The mode-locked laser achieved 3-dB spectral bandwidth of 24.56 nm centered at 1562.7 nm, with an output power of 5.0 mW and a pulse energy of 16.81 nJ. The DSR pulse tunability was optimized, where the pulse width was extended from 20 ns to 140 ns, demonstrating enhanced performance with a repetition rate of 297.3 KHz. The optimization was achieved through careful figure-of-eight NALM cavity design, precise polarization control and progressive pump power tuning under net anomalous dispersion

Signal to Noise Ratio Performance Analysis for Vibration Detection Using Phase Sensitive OTDR in Distributed Acoustic Sensing

Muhsin Muhsin — 2025-12-01

Phase-sensitive optical time-domain reflectometry (Φ-OTDR) has emerged as a powerful technique for distributed acoustic sensing (DAS) in a wide range of applications, including perimeter security. The signal-to-noise ratio (SNR) is a critical parameter in determining the sensitivity and reliability of vibration detection in these systems. In this paper, we present a detailed analysis of SNR performance in Φ-OTDR-based DAS systems. We investigate the influence of key system parameters such as optical pulse width, vibration frequencies and spatial resolution on the SNR value. A DAS setup is developed to evaluate how these parameters affect the backscattered signal and noise characteristics over pulse widths and vibration frequencies. Our results show that SNR increases exponentially with optical pulse widths, but it degrades the spatial resolution value. The findings provide practical insights into the phase information in the development of a more efficient and sensitive DAS system. This work contributes to the growing understanding of SNR limitations and enhancement strategies in distributed fiber optic sensing.

Temperature Dependence of the Brillouin Frequency Shift (BFS) using Independent Real Spectral Analysis in DCS-BOTDR Fiber Sensor

Ain Nabihah Mohammad Rihan — 2025-10-30

We propose an independent real spectral analysis method to improve the Brillouin frequency shift (BFS) resolution using the differential cross-spectrum technique (DCS-BOTDR). The proposed method only considers the real components to extract BGS. For a 1.2 km test fiber length, we have achieved 0.4 m spatial resolution, 1.98 MHz Brillouin frequency accuracy, and 1.025 MHz/°C temperature sensitivity using the proposed method.

Exploring LiDAR as a Scalable Photonic Alternative to Turbidimeters for Water Turbidity Monitoring

Nur Aina Athirah Mohd Nizar — 2025-11-05

Water turbidity is a critical parameter for assessing water quality, conventionally measured using turbidimeters that rely on nephelometric light scattering. While effective, these instruments are constrained to labor-intensive sampling, limiting spatial and delayed data analysis. This paper explores the potential of LiDAR which a photonics-based ranging technology as an alternative method for turbidity assessment. Both turbidimeters and LiDAR operate on light-particle interaction principles. In this research, a compact TFmini-S LiDAR sensor was used in a controlled laboratory setup to observe signal strength changes in relation to turbidity levels measured by a conventional turbidimeter. Though limited in range, the sensor will be use to demonstrate a relationship between signal attenuation and turbidity. These results will provide foundational support for the future use of LiDAR in scalable, non-contact, real-time turbidity monitoring. The study invites further exploration into adapting LiDAR for broader environmental water quality applications.

Dual-Side Polished PCF Structure as Refractive Index Sensor

Marinah Othman — 2025-11-05

This paper presents a dual-side polished photonic crystal fiber (PCF)-based structure designed for refractive index (RI) sensing applications. The sensor leverages a gold layer deposited on the PCF surface to excite surface plasmons, enabling highly sensitive detection of changes in the surrounding refractive index. Numerical simulations, utilizing COMSOL software, were conducted to analyze the sensor's performance for pitch variation between 3.0 µm and 4.0 µm of the PCF structure. The analysis focuses on the mode characteristics and electric field distribution within the sensor. The simulation results demonstrate the influence of the PCF pitch on the sensor's optical properties, highlighting its potential for accurate RI detection in various applications.

Comparative Study on Carbon Dots and Carboxyl-Carbon Dots - LSPR for Creatinine Detection

Athiyah Sakinah Masran — 2025-11-02

The detection of creatinine, a crucial biomarker for kidney function, has attracted significant attention due to the need for rapid and sensitive detection. In this study, we report a comparative analysis of Carbon Dots (CDs) and Carboxyl-Carbon Dots (CDsCOO) for developing a fluorescent-based creatinine sensor. Both carbon dots were synthesized via a hydrothermal approach, with surface modification introduced to generate carboxyl functional groups in CDsCOO. Creatinine sensing performance was evaluated based on the fluorescence quenching response, calibration curve linearity, sensitivity, and limit of detection (LOD). The effectiveness of this material was evaluated at concentrations ranging from 0 to 0.6 mg/dL. The CDsCOO demonstrated superior performance with enhanced sensitivity and a lower LOD than unmodified CDs, achieving a LOD of approximately [0.05 mg/dL & 0.28 mg/dL] and a sensitivity of [20.123 ndL/g & 3.696 ndL/g]. This work highlights the potential of CDsCOO as a promising platform for efficient and selective creatinine detection.

Effect of MoS2 coated on tapered optical fiber for humidity sensor

Muhamad Afiq Aiman Mazlan — 2025-10-30

This study investigates the influence of tapered optical fiber diameter and MoS₂ concentration on the sensitivity of optical humidity sensors fabricated using the heat-and-pull method. Optical fibers with tapered diameters of 3 µm, 5 µm, and 7 µm were analyzed under varying humidity levels (40%, 50%, and 60%). Additionally, the effect of different MoS₂ concentrations 2 µl, and 4 µl coated on the fiber surface was examined for each diameter. Experimental results demonstrate that smaller fiber diameters yield significantly higher sensitivity, with the 3 µm fiber showing the greatest power response at all humidity levels-up to 35.07% more sensitivity at 40% humidity compared to 7 µm fibers. Furthermore, increasing MoS₂ concentration enhances the sensor response across all diameters, with the 4 µl concentration consistently delivering the highest power output. For example, at 40% humidity, a 4 µL concentration on a 7 µm fiber produced an 18.89% increase in sensitivity compared to an uncoated fiber. These findings highlight that both reduced fiber diameter and increased MoS₂ concentration significantly improve the sensitivity of optical humidity sensors, offering a promising approach for developing high-performance environmental sensing devices.

The Effect of Adaptive Resource Allocation Methods on Performance Metrics in the Load Balanced RoF System

Hasif Mahazir — 2025-12-01

In recent years a great attention has been captured by the researchers in 5G networks merging of radio frequency and optical fiber technologies known as Radio-over-Fiber (RoF) system which can provide cost-effective, and high-capacity wireless access network provisioning of broadband, interactive, and multimedia wireless services. It is a promising challenge to improve the network coverage and balancing the load of network resources specially in terms of densed wireless access network. This paper reviewed the existing works focusing on load balancing techniques both explicitly and implicitly for wireless network using RoF technology. It is noticeable that all the researchers have focused on different types of static and dynamic load balancing schemes based on logical resources like bandwidth, frequency, wavelength and physical network resources like number of remote radio heads, base stations and mobile unit or mobile users by using mathematical models, algorithms, reinforcement learning for both radio access network and could or software defined network using RoF technologies. All these works are evaluated for different parameters like bandwidth, latency, frequency, wavelength, delay, time, interference, and number of mobile units. But still there is scope for future work to focus on effective, efficient, scalable, dynamic, cost effective and also energy efficient load balancing mechanism for dense wireless access network using RoF for ensuring quality of service to the large growing population.

A Advancing Optical Sensing Through Tapered Optical Fiber and Tilted Fiber Bragg Gratings: Fundamentals, Trends, And Hybrid Possibilities

Abdulfatah Abushagur — 2025-12-01

A label-free optical biosensor presents an innovative solution for biochemical detection, besides tapered optical fiber (TOF), Tilted fiber Bragg gratings (TFBGs) have been shown to have distinctive properties that enable the creation of highly precise sensors, especially in biochemical realm, while maintaining cost efficiency in both manufacturing and signal interrogation. This review compares both the TFBGs and TOF, Emphasizing the latest developments in their fabrication techniques, sensing mechanisms, and limitations. Most recent achievements of both will be discussed through examples from the literature. Pros and cons will be assessed and discuss the potential advantages of combining both structures.

Fabrication and characaterisation of tapered and arc-shaped fiber for saturable absorber device in pulse fiber laser operation

Rizal Ramli — 2025-11-05

Pulse fiber lasers are recent developments that produce efficient pulse lasers by incorporating gain medium, saturable absorber (SA) materials and SA hosts. However, the SA hosts can be improved for stable generation pulse fiber laser. This discussion emphasizes the fabrication and characterisation of tapered and arc-shaped fiber using the flame-brushing and wheel polishing technique, respectively. Examples of using tapered fiber and arc- shaped fiber to generate Q-switched and mode-locked will be deliberated that can possibly be applied in communications, medicine and sensing.

Improve Formaldehyde Vapor Sensing

NORHAFIZAH BURHAM — 2025-12-01

Formaldehyde (CH₂O) is a toxic, colourless, and flammable gas that is widely used in various industries and household products. Current formaldehyde detection methods often suffer from limitations such as low sensitivity, high cost, and impracticality for widespread use in residential and industrial settings. This study focuses on evaluating the performance of uncoated and Rhenium Disulfide (ReS₂)-coated tapered optical fibers (TOFs) in detecting formaldehyde, using fibers with a waist diameter of 10 µm and a length of 3 mm. The experimental evaluation was conducted by exposing the TOFs to formaldehyde vapor concentrations of 1%, 2%, 3%, 4%, and 5%, under relative humidity conditions ranging from 30% to 90%. The results show that the ReS₂-coated TOFs demonstrated better sensitivity in detecting formaldehyde compared to uncoated TOFs with measured sensitivities of –0.03245 dBm/% and –0.00371 dBm/% at 5% formaldehyde concentration. Overall, formaldehyde sensing performance can be improved by coating the TOFs with ReS₂, with sensitivity increasing by more than 80% compared to the uncoated fibers.