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.

The torsional stiffness is one of the most important properties of chassis that significantly affect its dynamic characteristics such as handling and rollover. The torsional stiffness is desired to be as high as possible since low torsional stiffness may cause resonance or vibration. There are several types of heavy duty truck chassis that used in Malaysia and no information about the torsional stiffness magnitude of it. In this work, the torsional stiffness of several existing types of heavy duty truck chassis and some modified types, namely: arc model, block model, hole model, multi holes model and fully block model are determined using finite element method. The torsional stiffness of several chassis was compared together with the weight comparison in order to get the best design of chassis that has high torsional stiffness and low weight. Based on the simulation result, the multi holes model is the best design due to the highest of torsional stiffness and the lowest mass.

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The objective of this work is to analyze and optimize a bus frame structure using Finite Element Method in dynamic conditions. The bus body geometry was obtained directly from the three-dimensional Computer-Aided Design files. The optimization was conducted to determine the minimum weight of the bus frame structure without violating the specified natural frequency constraints. The design variable is the thickness of the bus body frame. In present study, Adaptive Single Objective method was chosen as an optimizer method. The results show that the structural weight of the bus frame can be reduced about 8% without changing its dynamic characteristic.

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.

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.

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This work presents optimization of the dimension of ridge waveguide structure to be used as temperature sensor. The objective of the work is to obtain an optimum dimension of ridge waveguide so that it provides high sensitivity to temperature. Ridge waveguide structure was chosen since it has strong light confinement and low bending loss. The optimization was done by simulating the temperature distribution and electric field distribution inside the waveguide using Finite Difference Method (FDM). The simulations were done for various waveguide width and waveguide thickness. The results showed that as the width increased, the sensitivity decreased. The optimum ranges of waveguide dimensions are between 10μm to 20μm and 15μm to 25μm for width and thickness, respectively.