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The research aims to determine the potential of tea waste as an environmentally friendly alternative acoustic material. The acoustic material is made by mixing tea waste powder with fox glue and water, formed, and dried. The acoustic material was made into six samples with different compositions of tea wastes, that were 20 g, 40 g, 60 g, 80 g, 100 g, and 120 g. The value of the effectiveness of noise reduction and the coefficient of sound absorption, both were obtained the most optimum in sample 6 with a composition of 120 g, that were 10.1% and 0.07497 dB. The value of both increases with the increase of the composition of the tea wastes in the acoustic material.

Temperature measurement is important in various applications; therefore, various temperature sensors have been developed. Due to its advantages, many optical fiber-based temperature sensors have been proposed. The wavelength modulation-based optical sensor is interesting due to high accuracy. However, the complex fabrication process and high cost limit the advantages of the sensors. Therefore, we proposed a simple and low-cost Mach Zehnder interferometer (MZI) sensor using step-index plastic optical fiber (SI-POF). Performance characterization of the sensor to temperature variation is presented. The sensor consists of two tapers at several distances, forming an interferometer. The first taper was designed to be steep to allow excitation of cladding modes, while the second taper was gradual to suppress power loss. Characterizations were done in terms of sensitivity, hysteresis, and repeatability by analyzing the output spectrums recorded by the spectrometer at various environment temperatures, 35oC to 85oC, with an increment of 10oC. The results showed that the sensor has a sensitivity of 0.0431 nm/oC and a correlation coefficient of 0.9965. Hysteresis of 6.9×10-3 was observed. In terms of repeatability, the sensor shows a maximum deviation, ±3oC, which was mainly resulted from the fluctuation of the oven temperature. Despite its high deviation, the sensor has advantages of simple fabrication, low cost, robust, and low power loss, which make it a good candidate for temperature sensors.

The study of stability and optical properties of the dye-sensitized solar cell (DSSC) based extract of Musa Acuminata bracts have been done.Banana flowers extract was used as photoactive material because it contains anthocyanin. This study focuses on the optimization of semiconductor, natural pigment, and the counter electrode.The ZnO coating used spray coating method. Anthocyanin and polyethylene glycol (PEG) coating were conducted using droplet method.Fabrication of plated copper counter electrode was performed using the electrochemical method. PEDOT:PSS electrolyte is coated on the final process after the two electrodes are coupled by inserting between the two electrodes. The highest efficiency reached 6.24x10-2%.

Investigation of refractive index (RI) and temperature response of unsaturated polyester resin (UPR)/polymethylmethacrylate (PMMA) based waveguides is presented. Three type waveguide structures were fabricated which are straight waveguide (sensor A), curved waveguide (sensor B) and half-filled core waveguide (sensor C). Simple fabrications were done by engraving PMMA sheets using CNC engraving machine to form grooves with cross section of 1 × 1 mm 2 . The grooves were then filled with UPR as core material. To investigate the RI response, the waveguides were immersed in glucose solution with various concentration values having RI of 1.33 to 1.3547. Meanwhile, for temperature response characterization, the sensors were placed in distilled water while heated using magnetic stirrer with temperature variation of 35°C-85°C with increment of 5°C. The results showed that the sensors showed good RI sensitivity and linearity with the highest sensitivity of -48.476 dB/RIU. It was also observed that the sensors were temperature dependent. The highest error due to temperature effect is -1.8 × 10 − 4 RIU/°C.

The purpose of this study is to obtain the optimum buried waveguide structure through modeling for refractive index sensor applications. The waveguide cladding material used as Polymethylmethacrylate (PMMA). The core cross-section size was 1 × 1 mm2. The simulation was carried out at a wavelength of 650 nm using the Finite Element Method (FEM). The parameter of the buried waveguide optimized in this model was the core refractive index and the thickness of the upper cladding to obtain a high propagation constant and good sensitivity to refractive index. Modeling was done for various core refractive index values ​​varied in the range of 1.52 to 1.59, which are the refractive index of various types of polymers. To optimize the sensitivity, the thickness of the upper cladding was varied between 0.125mm to 0.5mm. Besides, a simulation was also carried out for a waveguide without an upper cladding. The results show that the optimum waveguide is a waveguide without upper cladding using polyester as core material with a refractive index value of 1.57 and a sensitivity of 4.9 × 10-10rad /m. RIU.

This paper presents characterization of optical temperature sensor using step-index plastic optical fiber (SI-POF) in intrinsic Mach Zehnder interferometer (MZI) structure. The MZI was developed by forming two tapers at several distance. By exploiting the wavelength dependency of spectrum intensity, measurement was done by using intensity based measurement at two different wavelengths. Characterizations were done to obtain the sensor performance which were sensitivity and hysteresis. The characterization was carried out by launching white LED to the sensor while the sensor was in temperature controlled-oven. The output spectrum was observed at the other sensor tip using spectrometer at various temperature which are 35°C to 85°C with increment of 10°C. It was found that the sensor has sensitivity and hysteresis of 1×10−3/°C and 1.97×10−2, respectively.

Viscosity determination is necessary in variety of applications such as evaluation of environmental pollution, chemical analysis, and as a material quality assessment. Optical fiber-based viscosity sensors are interested since it has various advantages compared to conventional viscosity sensors such as free from electromagnetic interference, compact and could be applied in hazard environment. This study aims to study the performance of back scattering method based viscosity sensor using optical coupler. The sensor design consists of 2×2 plastic optical fiber coupler connected with un-cladded POF as sensor head (sensor A). Characterization was done by connecting 660 nm LED as light source to the one of the coupler branch and an Ocean Optic USB4000 spectrometer to the other branch as light detector. Meanwhile, the sensor head was immersed in glycerin solution. The glycerin solution concentration was varied for various concentration which are 40%, 50%, 60%, 70%, and 80%. Sensor head without the use of optical coupler was fabricated and characterized as comparison (sensor B). The results show that sensor A has a better performance compared to sensor B in terms of linear range. The sensitivity of sensor A is -0.88584 dB/mPa.s at working range of 8.765-57.265 mPa.s with a correlation coefficient of 95.72%.

This work presents synthesization and characterization of polyester resin doped with lead acetate (Pb (CH3COO)2) as an alternative material for radiation protection in radiography. Five samples were synthesized with various lead concentration which are 0%, 3.5%, 3.75%, 4% and 4.5%. The samples were characterized using X-ray, He-Ne laser, and FTIR. The results showed that as lead concentration was increased, optical density increased while X-ray transmission decreased. It were found that the attenuation coefficients for each samples were 0.132 cm−1, 0.435 cm−1, 0.543 cm−1, 0.691 cm−1, and 1.156 cm−1. In terms of transmission and attenuation coefficient, lead-polyester composite with lead concentration of 3.5% has an optimum performance.

This study presents the fabrication and characterization of polymethylmethacrylate (PMMA)-based buried waveguide for operation in the visible light range. The fabrication was done by engraving PMMA sheet using a computer numerical control (CNC) machine to be filled with a waveguide core material and then covered with PMMA sheet. The material used for waveguide core were Unsaturated Polyester Resin (UPR) with the brand of Yukalac C108B and Eternal 2441IP. Characterization was done to determine the output power loss by passing light from an LED with wavelength of 660 nm into the waveguide. The output spectrum was observed using a spectrometer. The results showed that power loss for waveguide with Yukalac C108B and Eternal are -7.89 dB and -13.85 dB, respectively.

This work presents simulation of light propagation inside tapered structure-plastic optical fibre (POF) subjected to various surrounding temperatures and refractive index (RI). The tapered structure served as Mach-Zehnder interferometer (MZI) which split light into core modes and clad modes that recombined at the end of the taper. Simulation was done by using Beam Propagation Method (BPM) solved using Finite Difference Method (FDM). The light launched in to the MZI was varied from 611nm to 655nm. In order to give temperature effect, the temperature was varied from 30°C to 80°C with increment of 10°C. The results showed that the free spectral range (FSR) of the MZI are shifted as temperature increased. The sensitivity for the peak and dip of the FSR are -0.0158 nm/°C and -0.0153 nm/°C, respectively. For RI sensitivity investigation, the surrounding RI was varied from 1.333 to 1.349. The sensitivity of peak FSR and dip FSR to RI change are -98.638 nm/RIU and 105.4 nm/RIU. Therefore, the MZI can be used to measure RI and temperature simultaneously.

The presence of mercury ions is a serious threat to human health and environment. Water consumption containing mercury is very dangerous for human healt. The purpose of this work is to design a heavy metal sensor ion using plastic optical fiber to detect mercury ions in water. The sensor was fabricated by coating the optical fiber by chitosan through dip-coating technique. There are three diameter of optical fiber sensor that was fabricated, which are 1087.64 μm (sensor A), 1691.64 μm (sensor B) and 1736.33 μm (sensor C). Sensor characterization was done by connected the tip of plastic optical fiber to an LED and the other tip was connected to a photodioda. The results show that sensitivity of sample A is 0.32 mA/ppm, sample B is 0.56 mA/ppm and sample C is 0.64 mA/ppm. In terms of respone time, it is shown that thr respon time for sensor A, B and C are 22 s, 42.5 s and 86 s respectively.

Mach Zehnder interferometer (MZI) based on plastic optical fiber (POF) is interesting due to its robustness and simple fabrication. In this work, MZI-POF was designed and its sensitivity to temperature change was characterized to investigate its performance for sensor application. The MZI-POF was fabricated by forming two tapers at several distance by simple heat-pull method. The spectra was investigated by launching white light emitting diode (LED) and the output were observed using VIS-NIR spectrometer. It is shown that the wavelength of spectrum peak and spectrum dip were shifted compared to that of un-tapered POF which indicates that the structure serves well as MZI. Sensor sensitivity to temperature was determined by measuring the spectrum for various temperature which was varied from 40°C to 80°C with increment of 5°C. The result showed that the sensor sensitivity is 0.0693nm/°C in terms of peak measurement and 0.0487nm/°C for dip measurement. Therefore, MZI-POF is a potential candidate for temperature sensor.

A new sensor for simultaneous measurement of humidity and temperature is proposed. The sensor consists of Fabry–Perot cavity formed by two identical uniform fiber Bragg gratings. To make the cavity serves as humidity sensor, moisture sensitive polymer, which is polyimide, is coated on the FBG and on the cavity with different thickness. When the sensor is exposed to the relative humidity change, the polyimide will expand and stretch the fiber and induces strain on the FBG and on the cavity. The induced strain alters the grating period, cavity length and effective refractive index of fiber. The simulation results show that the humidity sensitivity and thermal sensitivity are 1.92 pm/%RH and 8.87 pm/°C, respectively, for polyimide coating thickness of 10 μm on the FBG and 15 μm on the cavity.

This paper presents the stress analysis in optical fiber due to swelling of hydrogel material coated on it. The silica optical fiber was assumed to be coated by hydrogel that consists of hydroxyethyl methacrylate, acrylic acid and ethylene glycol dimethacrylate as crosslinker. The hydrogel swelling was modeled using free energy function. The conditional equilibrium of hydrogel was solved using finite element method and the stress induced in optical fiber was simulated simultaneously. The simulations were done for two hydrogel coating thickness values, 30 µm and 40 µm. Etched optical fiber coated by 40 µm hydrogel was also simulated. The results show that maximum stress in optical fiber is higher for thicker hydrogel thickness and is higher for etched optical fiber. Maximum stress magnitudes at all pH values are below tensile strength of optical fiber.

The 2 × 2 polymer thermo-optic switch based on MMI coupler is realized. This device is fabricated using standard fabrication techniques such as coating, photolithography, and dry etching. A crosstalk level of −36.2 dB is achieved at cross and bar states. A power consumption of 1.85 mW is applied to change the state of the switch from the cross to the bar state. A switching time of less than 0.7 ms is traced to change a state of the realized switch.

The 2 £ 2 MMI polymer thermo-optic switch in a high refractive index contrast (0.102) with a new structure design is realized. This device was fabricated using standard fabrication techniques such as coating, photolithography, and dry etching. A crosstalk level of i36:2dB has been achieved. Meanwhile the extinction ratio of 36.1dB has been achieved in this device. The polarization dependent loss (PDL) of 0.3dB and Insertion loss of 1.4dB were measured at 1550nm wavelength. In terms of wavelength dependency, the device shows a good performance within C-band wavelength with vacillation of the insertion loss value around 0.88dB. The power consumption of 1.85mW was measured to change the state of the switch from the cross to bar state. The measured switching time was 0.7ms.

A 2 × 2 MZI–MMI switch based on thermo-optic effect with a ridge in the silicon substrate was proposed and the performance of switch was simulated. The main purpose behind this change in substrate layer is to localize the heating at a heated arm single mode waveguide and limit the increasing temperature at a second one. The switch performance of the device should be improved, compare to the usual one. Using finite difference beam propagation method (FD-BPM) and thermal computing simulation based on finite element method (FEM), the results clearly indicate that the MZI–MMI switch can satisfy −31 dB crosstalk at two states.

A novel thermo-optic multimode interference (MMI) switch with air and silicon trenches was proposed, and the performance of the switch was simulated. In the design, one heating electrode is used to alter the refractive index at a spot image which changes the phase of this image to realize the switching function. The simulation results clearly indicate that the MMI switch can satisfy −39 dB crosstalk at two states. The electric power consumption for the MMI switch with these trenches is less than half of that of a conventional MMI switch.

Evanescent wave based-optical fiber sensor to detect cadmium ion is proposed. Chitosan was used by using the dip-coating method. The sensor was fabricated in U-bent shape. U-bent optical sensor at aconcentration of 2ppm and 5ppm had asensitivity of 0.2067 dBm/ppm and -0.7995 dBm/ppm, respectively. At a level of 2ppm - 5ppm, the optical sensor has a linear response with asensitivity of -0.283 dBm/ppm. The sensor takes 9.5 minutes to reach steady stateat aconcentration of 1 ppm. Atalevel of 2ppm - 5ppm, the sensor takes 5 minutes to 10.45 minutes to reach steady state.

A wavelength modulated optical pH sensor is presented. The sensor comprises fiber Bragg grating (FBG) coated with pH sensitive hydrogel. The sensing principle relies on wavelength shifts resulted from the induced strain on the FBG due to mechanical expansion of the hydrogel. The pH response of the sensor was simulated using free energy function by employing finite element method. Experimental work was carried out to investigate the pH response, time response, and temperatures cross sensitivity of the sensor. The results show that the sensor has a good reversibility and provides linear response in pH range of 5 to 7 with sensitivity of 0.114nm/pH unit.

This paper present the modeling and simulation of the hydrogel coated FBG for pH sensor application. The hydrogel swelling was modeled by using Poisson-Nernst-Planck equation and mechanical equilibrium equation. The simulation was done by assuming that the hydrogel was coated on unetched fiber and etched fiber. The strain induced at the fiber core was analyzed using finite element method. It was found that at the region near the jacketed fiber, the strain is distributed nonuniformly. The non uniform area for etched fiber is shorter than that of unetched fiber. The Bragg wavelength shift due to strain of the etched fiber is much larger than that of the unetched fiber.

This paper demonstrates the analysis of fiber Bragg grating properties due to hydrogel coating swelling effect. The modeling was done by simulating the hydrogel swelling behavior, and then carried out strain and stress analysis induced on the fiber due to hydrogel expansion. Meshless numerical method was adopted to solve the Poison Nernst Planck equation coupled to mechanical equation to simulate the hydrogel swelling. The hydrogel coating thickness was varied for 4 values, namely 30 μm, 40 μm, 50 μm and 60 μm. The strain and stress analysis were done numerically using finite element method. The results show that the strain on the fiber increases as the hydrogel coating thickness increased. The increase of hydrogel thickness results in the improvement of sensor sensitivity at the expense of stress value.

In environmental or safety monitoring, continuous on-line systems are generally desired and fiber optic sensor (FOS) networks are well-suited for this purpose, with capability for large area coverage. The advantages of FOS are freedom from electromagnetic interference, wide bandwidth, compactness, and geometric versatility. Deployment of distributed and array sensors covering extensive structures and geographical locations is also feasible. This is particularly true when Bragg grating based fiber sensors is considered in view of their highly favorable characteristics. The basic principle of operation commonly used in a FBG based sensor system is to monitor the shift in wavelength of the reflected “Bragg” signal, λ B , with the changes in the environment, e.g. strain, temperature. Most of the FBG-based sensors reported in the literature are designed for strain and temperature measurements [1,2,3]. These sensors are designed for distributed embedded structural strain sensing in bridges, roads, ships and buildings, etc. Chemical fiber optic sensors are also extensively developed [4].

Optical couplers are important components for signal distribution in optoelectronic transmitter/receiver modules. Y-junction waveguide is an attractive candidate for optical coupler due to its less wavelength and polarization dependent. However, they suffer from excess loss due to the mode field/wave-front mismatch between the output and input branches. Furthermore, the difference between the outputs according to the mismatch of the optical signal further increases when the optical signal is a multi-channel signal. In addition to the loss due to the mode mismatch, the connection loss due to the corner-bent waveguide also occurs in a conventional Y-branch. Various methods have been proposed to reduce the junction excess loss by modifying the physical geometry of the Y-junction directly. The Y-junction power divider geometry with asymmetry waveguide structure by increasing the rib height of the waveguide only from the inner side of the branches has been proposed [1]. Gamet and Pandraud [2] proposed segemented silica waveguides to reduce loss of the Y-branch. This paper presents optical coupler which is formed of segmented waveguide to reduce effective refractive index in the branching region and modified cosine S-bend to provide smooth connection to the tapered waveguide.

The performances of various apodization profiles, namely Gaussian, raised sine and hamming function for unchirped fiber Bragg grating are presented. The performances investigated include reflectivity, full width half maximum bandwidth, and sidelobe level. Transfer matrix method was adopted to solve the coupled mode equation to simulate the spectral profile of the apodized fiber Bragg gratings. The apodization performances were investigated under various refractive index modulation values and various grating length values. The results show that Gaussian profile suppresses sidelobe level much more efficiently than raised sine and hamming function.

A thermo-optic multimode interference (MMI) switch with a ridge structure on top of the MMI and also introducing another ridge in the silicon substrate was proposed and the performance of the switch was simulated. In the design, one heating electrode is used to alert the refractive index at spot image which change the phase of this image to realize the switching function. The simulation results indicate that the MMI switch can satisfy 39dB crosstalk at two states. The electric power consumption for the MMI switch with these ridges is less than half of that of a conventional MMI switch.

A new optical pH sensor based on fibre Bragg grating (FBG) is demonstrated. The sensor consists of a FBG coated with pH sensitive hydrogel. The sensing was performed through the detection of wavelength shifts resulting from the induced strain on the FBG due to mechanical expansion of the hydrogel. An elastomeric coating was applied before the hydrogel coating to improve the sensitivity. The sensor performance was investigated by simulating the hydrogel swelling and the strain induced on the FBG. The swelling of hydrogel due to pH change was modelled using a free-energy function and was solved using the finite element method. With silicone rubber as the elastomer material, the results show that the sensitivity was improved by up to 66% compared to that of the FBG pH sensor without elastomeric coating.