Sahbudin Shaari

The ray tracing of unclad U-shape multimode fiber optic is examined by using Zemax simulation have been proposed. The influence of the geometry of sensing region such as absorbing medium refractive index, n₂, shape of fiber and the bending radius is analyzed. Number of analysis ray is determined and the value of n₂ is varied at 1, 1.3314, 1.359, 1.36, 1.37 and 1.4. The intensity of light propagate inside the fiber is reducing at high n₂ and this graph pattern is supported by experimental result. A U-shaped sensor is used for the analysis because of the sensitivity is higher than straight fiber design due to their higher penetration depth. Zemax simulation shows that the fiber with bending radius 1.5 mm has higher response compared to fiber with radius 2.5 mm.

Zinc oxide film has been fabricated by converting flower-like structure of zinc carbonate hydroxide made by chemical bath deposition technique. Flower-like structure is employed as charge transport network of dye-sensitized photoanode. Analysis of current density–voltage characteristic shows deposition temperature and deposition time of chemical bath deposition influence photovoltaic performance. Analysis of electrochemical impedance spectroscopy reveals short electron lifetime and high effective electron diffusion coefficient of zinc oxide-based dye-sensitized solar cell.

A method to fabricate optical fiber microprobe by using manual fusion splicer has been developed. Electric arc heating and one-sided pulling technique was applied in order to produce sharp tips. Small diameter of probe tip can be produced using low value of discharge current and heating time. By setting the discharge current at 8 mA and heating time at 4.43 s on the fusion splicer, small tip dimension as small as 1.47 μm was fabricated where 60% of the tip dimensions were within 1.00 μm to 6.00 μm.

The optimum transmit power for an optical code division multiple access (OCDMA) system based on enhanced double weight (EDW) code is evaluated for various transmission distances considering the nonlinear stimulated Brillouin scattering (SBS) effects. It has been observed through computer simulation that SBS causes backward scattering of transmit signal and this in turn causes a reduction of received power and limitation improvement for the bit error rate. It has been shown that the longer transmission distance have low Brillouin threshold power value and the power launched require must not excess the threshold power in order to overcome SBS effects. Also in this paper, we investigate and demonstrate how the attenuation coefficient and effective core area of optical fiber transmission influence the Brillouin threshold power in optical CDMA system.

We apply the arrayed waveguide grating (AWGs) method for encoder and decoder design for complete transmitter and receiver system. The encoder and decoder module will be using the AWG to encode and to decode optical source into useful signal to carry the data and transmit it using a single optical fibre. This module was designed to suite the zero cross correlation (ZCC) code. In this paper the study conduct to design of encoder/decoder for optical code division multiple access (OCDMA) system based AWGs and performance of ZCC code using this system. Results demonstrate that the encoder/decoder design of ZCC code using AWGs is capable of up to 100 km with BER less than 10^-9 which is typically allowed in optical communications.

In this paper, we present a theoretical analysis of the noise resulting from cross-phase modulation in an optical WDM transmission system. Analytical approach has been used to evaluate the bit error rate (BER) performance limitation of a WDM transmission system imposed by crosstalk due to cross-phase modulation and the influence of changing channel spacing for various fiber types on the (BER) and the cross-phase modulation noise. Mathematical expressions are derived and solved that describe this fiber nonlinearity impairment in a multi-channel optical fiber network with highlighting the mitigation techniques. Numerical results demonstrate the validity of the analysis and theoretical expressions to have an insight about this nonlinear effect under investigation.

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