M. B. Othman

Comparison of wavelength propagation for Free Space Optical Communications

This paper presents the effect of atmospheric attenuation during severe hazy days for free space optical communications. The usage of free space optical communications is still rare in Malaysia due to environment factor. The FSO technology is also known as unguided beam or dasiaoptical wirelesspsila or infrared broadband. This study offers quick preliminary investigation on possible FSO performance based on wavelength selection before final commissioning and installation at site. Thus, FSO installers could make quick judgment before giving recommendation of a suitable wavelength to the customers. Preliminary evaluation of system performance of system performance is done by using local weather data obtained from metrological department. Current study among designers and FSO users show that 1550 nm light produce less atmospheric attenuation in the transmission under all weather conditions. In this study, a suitable wavelength for FSO system is found for a particular site in low visibility. The best wavelength selection would result in optimized quality of FSO transmission in hazy conditions.

2x2 MIMO-OFDM Gigabit fiber-wireless access system based on polarization division multiplexed WDM-PON

We propose a spectral efficient radio over wavelength division multiplexed passive optical network (WDM-PON) system by combining optical polarization division multiplexing (PDM) and wireless multiple input multiple output (MIMO) spatial multiplexing techniques. In our experiment, a training-based zero forcing (ZF) channel estimation algorithm is designed to compensate the polarization rotation and wireless multipath fading. A 797 Mb/s net data rate QPSK-OFDM signal with error free (<1 × 10(5)) performance and a 1.59 Gb/s net data rate 16QAM-OFDM signal with BER performance of 1.2 × 10(2) are achieved after transmission of 22.8 km single mode fiber followed by 3 m and 1 m air distances, respectively.

Analysis of the effect of haze on free space optical communication in the Malaysian environment

This paper presents the effect of atmospheric attenuation during hazy days for free space optical (FSO) communication in point-to-point connection. The analysis focuses on scattering coefficient and atmospheric attenuation effects on low visibility, which falls in the range of 1.8 km to 4.5 km. The performance comparison is also done for the wavelength of 850 nm and 1550 nm. The result shows that the performance of 1550 nm is better than 850 nm in both performance parameters. As the link range between transmitter and receiver increases, the atmospheric attenuation increases too. Deployment distance of less than 1km can reduce the effect of atmospheric attenuation. These challenges limit FSO to the short distance application.

MIMO-OFDM WDM PON with DM-VCSEL for femtocells application

We report on experimental demonstration of 2x2 MIMO-OFDM 5.6-GHz radio over fiber signaling over 20 km WDM-PON with directly modulated (DM) VCSELs for femtocells application. MIMO-OFDM algorithms effectively compensate for impairments in the wireless link. Error-free signal demodulation of 64 subcarrier 4-QAM signals modulated at 198.5 Mb/s net data rate is achieved after fiber and 2 m indoor wireless transmission. We report BER of 7x10(-3) at the receiver for 16-QAM signals modulated at 397 Mb/s after 1 m of wireless transmission. Performance dependence on different wireless transmission path lengths, antenna separation, and number of subcarriers have been investigated.

Voice control of home appliances using Android

This paper presents the development of home appliances based on voice command using Android. This system has been designed to assist and provide the support to elderly and disabled people at home. Google application has been used as voice recognition and process the voice input from the smart phone. In this paper, the voice input has been captured by the android and will be sent to the Arduino Uno. Bluetooth module in Arduino Uno received the signal and processed the input signal to control the light and fan. The proposed system intended to control electrical appliances with relatively user-friendly interface and ease of installation. We have demonstrated up to 20 meter of range to control the home appliances via Bluetooth.

Experimental demonstration of 5-Gb/s polarization-multiplexed fiber-wireless MIMO systems

We experimentally demonstrate a 5-Gb/s fiber-wireless transmission system combining optical polarization-division-multiplexing (PDM) and wireless multiple-input, multiple-output (MIMO) spatial multiplexing technologies. The optical-wireless channel throughput is enhanced by achieving a 4b/s/Hz spectral efficiency. Based on the implementation of constant modulus algorithm (CMA), the 2×2 MIMO wireless channel is characterized and adaptively equalized for signal demodulation. The performance of the CMA-based channel adaptation is studied and it is revealed that the algorithm is particularly advantageous to the MIMO wireless system due to the inter-channel delay insensitivity. The hybrid transmission performance of 26km fiber and up to 2m wireless MIMO is investigated.

Using CAP dimensionality for service and user allocation for optical access networks

The usability of carrierless amplitude and phase (CAP) modulation dimensions for service and user allocation for WDM optical access is experimentally demonstrated in a 2X2D-ODMA configuration.

Comparison of detection techniques in optical CDMA access network for point to multipoint configuration

In this paper, we are proposing a detection scheme known as spectral direct detection technique implemented with fiber bragg grating (FBG) act as encoder/decoder. This FBG based is used to encode and decode the spectral amplitude coding namely modified double weight (MDW) code in optical code division multiple access (OCDMA). This code is used due to its flexibility where its weight can be any even number that greater than two. Moreover, it can maintain the cross-correlation parameter equal to one. The performance of spectral direct detection technique against AND-subtraction technique which is both implemented with FBG based encoder/decoder is compared via simulation in downstream and upstream access network at point to multipoint (P2MP) configuration. The simulation will be carried out using OptiSystem version 6.0 and the performance is characterized through bit error rate (BER) and power received at various bit rate.

Spectral amplitude coding OCDMA using AND subtraction technique

A new detection scheme, namely AND subtraction technique is proposed and presented in this paper. The theory is being elaborated and the calculated and simulation results have been done by comparing AND subtraction technique against complementary subtraction technique by using DW code. In this paper we have proved that AND subtraction technique gives better bit error rate (BER) performance than complementary subtraction technique.

Comparison of carrierless amplitude-phase (CAP) and discrete multitone (DMT) modulation

We compare the transmission of 1.25 Gb/s CAP-16 and 909.2 Mb/s 16-QAM-DMT modulation formats over 2.4 km of MMF with 850 nm DM-CSELs. CAP displays 0.7-1.1 dB better sensitivity than DMT in this experiment.