Dr. Angela Amphawan | Massachusetts Institute of Technology (MIT) (original) (raw)

Websites by Dr. Angela Amphawan

Research paper thumbnail of QS University World Ranking Top 600

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Research paper thumbnail of Optical Technology Research Laboratory

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Research paper thumbnail of Universiti Utara Malaysia

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Research paper thumbnail of University of Oxford- Department of Engineering

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Publications by Dr. Angela Amphawan

Research paper thumbnail of 2 x 20 Gbps - 40GHz OFDM Ro-FSO transmission with mode division multiplexing

Journal of European Optical. Society Rap. Public. 9, 14041 (2014), Sep 2014

Radio-over-Free-Space-Optics (Ro-FSO) is a promising technology for future wireless networks. In ... more Radio-over-Free-Space-Optics (Ro-FSO) is a promising technology for future wireless networks. In this work, we have designed a hybrid orthogonal frequency division multiplexing (OFDM) Ro-FSO system for transmission of two independent channels by mode division multiplexing. Two independent 40 GHz radio signals are optically modulated at 20Gbps by mode division multiplexing of two laser modes LG00 and LG10 and transmitted over a free-space link of 20 km to 100 km. The performance of proposed Ro-FSO system is also evaluated under the effect of strong atmospheric turbulences

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Research paper thumbnail of The Role and Challenges of Free-space Optical Systems

Journal of Optical Communications, Jul 24, 2014

Complementing wireless radio networks with free-space optics (FSO) achieves high data rates by mo... more Complementing wireless radio networks with free-space optics (FSO) achieves high data rates by modulating radio subcarriers over an optical carrier without expensive optical fiber cabling, enabling a pervasive platform for reaching underserved areas. In this paper, we review the main features of FSO for terrestrial and inter-satellite communications. Simulations of 1 Gbps data transmission through FSO links in both terrestrial and inter-satellite communications have been investigated to highlight potential atmospheric challenges in FSO.

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Research paper thumbnail of Realization of free space optics with OFDM under atmospheric turbulence

Optik, Volume 125, Issue 18, Pages 5196–5198, Sep 2014

Free space optics (FSO) technology provides a promising solution for future broadband networks, o... more Free space optics (FSO) technology provides a promising solution for future broadband networks, offering high data transmission compared to RF technology. This work is focused on investigating the performance of an FSO system with OFDM and QAM. A 10 Gbps data stream is transmitted using a 4-level QAM sequence through the FSO system under different atmospheric conditions. Results indicate that the integration of SOA prolongs the maximum achievable distance with acceptable SNR to 185 km under clear weather conditions whereas under atmospheric fog, the maximum distance is extended to 2.5 km

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Research paper thumbnail of Selective Mode Excitation in SCM-OCDMA

International Conference on Photonics (ICP2013), Oct 2013

A six-channel 2.4GHz subcarrier multiplexing - optical code division multiple access (SCM-OCDMA) ... more A six-channel 2.4GHz subcarrier multiplexing - optical code division multiple access (SCM-OCDMA) system in conjunction with the selective excitation of LP01 and LP02 modes is presented for a multimode fiber Local Area Network. Simulation results demonstrate that mode selectivity increases the bandwidth-distance product and improves the BER performance of the channel.

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Research paper thumbnail of A Stepping Stone Perspective to Detection of Network Threats

International Journal of Applied Mathematics and Informatics, , Issue 3, Vol. 7, pp. 97 – 106, Oct 1, 2013

Current computing trends such as cloud computing, file sharing and social networking promote co... more Current computing trends such as cloud computing,
file sharing and social networking promote collaboration and allow greater mobility for users. Nevertheless, these computing trends increase the vulnerability of networks to security threats and challenge network resources. An ingenious technique employed by attackers for retaining anonymity is by exploiting intermediary host computers or stepping stones to instigate attacks on other computers. This paper explores novel application of the stepping stone detection concept in addressing network threats such as spams, backdoors, proxy server intrusions and denial of service attacks. Preliminary stepping stone detection models for each security threat will be constructed and the potential detection process is delineated. These preliminary concepts and models may prove useful for further optimization of network security in conjunction with other conventional detection techniques.

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Research paper thumbnail of Fitness Value Based Evolution Algorithm Approach for Text Steganalysis Model

International Journal of Mathematical Models and Methods in Applied Sciences, May 2013

In this paper, we present a new alternative method for text steganalysis based on an evolution al... more In this paper, we present a new alternative method for text steganalysis based on an evolution algorithm, implemented using the Java Evolution Algorithms Package (JEAP).The main objective of this paper is to detect the existence of hidden messages ased on fitness values of a text description.It is found that the detection performance has been influenced by two groups of fitness values which are good fitness value and bad fitness value. This paper provides a valuable insight into the development and enhancement of the text steganalysis domain.

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Research paper thumbnail of Performance Studies of Integrated Network Scenarios in a Hospital Environment

International Journal of Information Communication Technologies and Human Development (IJICTHD), Jun 2014

Hospital network is evolving towards a more integrated approach by interconnecting wireless techn... more Hospital network is evolving towards a more integrated approach by interconnecting wireless technologies into backbone networks. Although various integrated network scenarios have been published in the networking literature, a generic hospital model has not yet been fully explored and it remains a challenging topic in practice. One of the problems encountered by network practitioners is the seamless integration of network components into healthcare delivery. A good understanding of the performance of integrated networks is required for efficient design and deployment of such technologies in hospital environments. This research paper discuss on the modelling and evaluation of integrated network scenarios in hospital environments. The impact of traffic types (e.g. data, voice and video), traffic load, network size and signal strength on network performance is investigated by simulation. Three piloted case studies look at client performance in radiology Accident and Emergency (A & E and Intensive Care Unit (ICU)) scenarios. Each scenario reflects the need for various traffic types that end up distinct network behaviours. In the radiology scenario, email and File Transfer Protocol (FTP) traffic is found to perform well for medium-to-large networks. In the A & E scenario, Voice over Internet Protocol (VoIP) traffic is shown to generate very limited jitter and data loss. The performance is aligned with the Quality of Service (QoS) requirements. In the ICU scenario, the performance of video conference degrades with network size, thus, a QoS-enabled device is recommended to reduce the packet delay and data loss. IEEE 802.11a suits in hospital environment because it mitigates interference on the 2.4GHz band where most wireless devices operate.

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Research paper thumbnail of Hospital Environment Scenarios using WLAN over OPNET Simulation Tool

International Journal of Information Communication Technologies and Human Development (IJICTHD), Jun 2014

For the past ten years, heterogeneous networks wired and wireless had tended to integrate seamles... more For the past ten years, heterogeneous networks wired and wireless had tended to integrate seamlessly, offering
effective and reliable service for medical operations. One of the problems encountered by network practitioners is the seamless integration of network components into healthcare delivery. As a multiplexing hospital model, the implementation certainly presents some challenges. The major technical and performance issues involve are as following. The operating parameters should keep aligned to the Quality of Service (QoS) requirement throughout simulation. Bandwidth utilisation of wireless networking is a challenging issue for real-time multimedia transmission. IEEE 802.11 provides relatively lower data rate than wired networks, thus the developer tends to adopt a more compromised solution: either reduce the file size or compress the image packets. Communication performance that varies constantly with the impact of signal strength, traffic load and interference. As stated radio signal senses as a curve and attenuates greatly while metallic object and
microwave exist within the active range. To ensure devices do not interfere with other electronic equipments (e.g. heart monitors), assert wireless spectrum has to be managed appropriately. This research paper aims to develop a generic hospital network scenarios using Wireless Local Area Network (WLAN) over OPNET Simulation, to evaluate the performance of the integrated network scenario for Intensive Care Units (ICU). This research makes use of computer simulation and discusses various aspects of the network design, so as to discover the performance behaviour pertaining to effect of traffic type, traffic load and network size. In the ICU scenario, the performance of video conference degrades with network size, thus, a QoS-enabled device is recommended to reduce the packet delay and data loss. IEEE 802.11a suits in hospital environment because it mitigates interference on the 2.4GHz band where most wireless devices operate. Experiment examines the effect of signal strength in WLAN. It is convinced that -88dBm is the best signal strength threshold. Although 802.11a generates slightly lower throughput than 802.11g, this issues can be addressed by placing more APs in the service area. It is convinced that 802.11a suits the hospital environments, because it mitigates interference on the popular 2.4GHz band where most wireless devices operate. It is important for medical devices which require future upgrade and Bluetooth deployment.

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Research paper thumbnail of Anonymity Handling and Sensor Object Modeling for Pervasive Environments using VISA Processing

International Journal of Information Technology & Computer Science, Volume 15 Issue No 1, Jun 2014

Pervasive computing devices are configured for anywhere at any time services to adapt the changes... more Pervasive computing devices are configured for anywhere at any time services to adapt the changes in the dynamic
environment with respect to the user mobility. The paper proposes a salient model for a log based anonymity handling
in pervasive networks. The model defines a resource registry and sensor object modeling. Associability between the
nodes are configured with an allied user interface in the environment. Resource registry refers to a record of
information about the sensor nodes. A log book is maintained to keep track of the service discovery issues. New device
enquiry, registration and adaption are major issues in such pervasive devices. These issues lead to unacknowledged
communication that causes anonymity. This paper defines and discusses the presence of anonymity in pervasive
environments due to aforementioned issues.

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Research paper thumbnail of Enhanced Probability Density Function Using APD in SAC-OCDMA Systems Based SPD Technique

2013 IEEE Symposium on Industrial Electronics and Applications (ISIEA 2013), Sep 22, 2013

This paper examines the avalanche photodiode (APD) gain impact on spectral-amplitude coding optic... more This paper examines the avalanche photodiode (APD) gain impact on spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems based single photodiode detection (SPD) technique. Numerical results are used for inspecting the APD gain influence upon the probability density function (PDF) and signal-to-noise ratio (SNR) performance. The usage of APD over positive-intrinsic-negative (PIN) photodiode accommodates more users with improved PDF and higher SNR.

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Research paper thumbnail of Selective excitation of LP01 mode in multimode fiber using solid-core photonic crystal fiber

Journal of Modern Optics, Impact factor 1.166, Volume 60, Issue 20,pp. 1675-1683, Dec 2013

To address the overwhelming bandwidth increase in premise backbones, an attractive alternative fo... more To address the overwhelming bandwidth increase in premise backbones, an attractive alternative for selective mode excitation in multimode fiber (MMF) using solid-core photonic crystal fiber (PCF) is presented. The power coupling efficiency, differential mode delay, and bit-error rate performance of several structural designs of solid-core PCF waveguides are investigated for the selective excitation of mode LP01 in a MMF. The achieved coupling efficiency into mode LP01 is above 90% for PCF profiles with seven rings.

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Research paper thumbnail of Comparison of single mode fiber and multimode fiber in deployment of SCM-OCDMA in Local Area Network

Key Engineering Materials, Advanced Materials Engineering and Technology II, Advanced Material Engineering & Technology, vol. 594-595, pp. 1037, Jan 2014

The integration of heterogeneous technologies promotes ubiquity and mobility. Optical code divisi... more The integration of heterogeneous technologies promotes ubiquity and mobility. Optical code division multiple access (OCDMA) may be deployed in conjunction to SCM to improve the spectral efficiency and enhance the data rate of subscribers in a Local Area Network (LAN). This paper compares the performance of multimode fiber to single mode fiber in the deployment of a SCM-OCDMA system with multi-diagonal (MD) codes in a LAN.

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Research paper thumbnail of Tiering effect of solid-core photonic crystal fiber on controlled coupling into multimode fiber

Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications VII, Shizhuo Yin; Ruyan Guo, Editors, Proceedings of SPIE Vol. 8847 (SPIE, Bellingham, WA 2013), 88470Y., Sep 25, 2013

To address the overwhelming bandwidth increase in premise backbones, an attractive alternative fo... more To address the overwhelming bandwidth increase in premise backbones, an attractive alternative for selective mode excitation in multimode fiber (MMF) using solid-core photonic crystal fiber (PCF) is presented. The power coupling efficiency, differential mode delay and bit-error rate performance of several structural designs of solid-core PCF waveguides are investigated for the selective excitation of mode LP01 in a MMF. The achieved coupling efficiency into mode LP01 is above 90% for PCF profiles with seven rings.

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Research paper thumbnail of APD Gain Effect on SAC-OCDMA System using Modified-AND Detection Technique

Journal of Theoretical and Applied Information Technology, Vol. 53 Iss. 3, pp. 467-471, E-ISSN 1817-3195 / ISSN 1992-8645 , Jul 31, 2013

This paper investigates the avalanche photodiode (APD) gain effect on spectral-amplitude coding o... more This paper investigates the avalanche photodiode (APD) gain effect on spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) system using a modified-AND subtraction detection in comparison to the conventional AND detection scheme. Analytical results are presented to investigate the APD gain impact on the bit-error rate (BER) performance. In addition, we confirm the influence of the APD over the positive-intrinsic-negative (PIN) photodiode on the system performance using data transmission simulations.

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Research paper thumbnail of Phase-Induced Intensity Noise Reduction with Improved Group Velocity Dispersion Tolerance in SAC-OCDMA Systems

International Journal of Engineering and Technology (IJET), Vol. 5 No. 1, pp. 95 - 100, Mar 2013

The demand for efficient optical communication systems has fuelled considerable research in devel... more The demand for efficient optical communication systems has fuelled considerable research in developing techniques for eradicating phase-induced intensity noise (PIIN) in spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA). This paper investigates the use of modified-AND subtraction detection technique to mitigate PIIN in SAC-OCDMA systems. The simulation results show that the modified-AND subtraction detection demonstrates better performance over the conventional AND detection approach. Furthermore, we have found that, from a transmission length of 40 km onwards, group velocity dispersion (GVD) degrades SAC-OCDMA system performance apparently. Dispersion compensating fiber (DCF) is used to lessen the influence of GVD caused by single mode fiber (SMF).

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Research paper thumbnail of Reducing BER of spectral-amplitude coding optical code-division multiple-access systems by single photodiode detection technique

Journal of European Optical Society. Rapid Publications, Vol. 8, 13022, Imp. Fac. 1.02, Mar 2013

In this paper, we present a single photodiode detection (SPD) technique for spectral-amplitude co... more In this paper, we present a single photodiode detection (SPD) technique for spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. The proposed technique eliminates both phase-induced intensity noise (PIIN) and multiple-access interference (MAI) in the optical domain. Analytical results show that for 35 simultaneous users transmitting at data rate of 622 Mbps, the bit-error rate (BER) = 1.4x10^-28 for SPD technique is much better compared to 9.3x10^-6 and 9.6x10^-3 for the modified-AND as well as the AND detection techniques, respectively. Moreover, we verified the improved performance afforded by the proposed technique using data transmission simulations

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Research paper thumbnail of QS University World Ranking Top 600

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Research paper thumbnail of Optical Technology Research Laboratory

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Research paper thumbnail of Universiti Utara Malaysia

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Research paper thumbnail of University of Oxford- Department of Engineering

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Research paper thumbnail of 2 x 20 Gbps - 40GHz OFDM Ro-FSO transmission with mode division multiplexing

Journal of European Optical. Society Rap. Public. 9, 14041 (2014), Sep 2014

Radio-over-Free-Space-Optics (Ro-FSO) is a promising technology for future wireless networks. In ... more Radio-over-Free-Space-Optics (Ro-FSO) is a promising technology for future wireless networks. In this work, we have designed a hybrid orthogonal frequency division multiplexing (OFDM) Ro-FSO system for transmission of two independent channels by mode division multiplexing. Two independent 40 GHz radio signals are optically modulated at 20Gbps by mode division multiplexing of two laser modes LG00 and LG10 and transmitted over a free-space link of 20 km to 100 km. The performance of proposed Ro-FSO system is also evaluated under the effect of strong atmospheric turbulences

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Research paper thumbnail of The Role and Challenges of Free-space Optical Systems

Journal of Optical Communications, Jul 24, 2014

Complementing wireless radio networks with free-space optics (FSO) achieves high data rates by mo... more Complementing wireless radio networks with free-space optics (FSO) achieves high data rates by modulating radio subcarriers over an optical carrier without expensive optical fiber cabling, enabling a pervasive platform for reaching underserved areas. In this paper, we review the main features of FSO for terrestrial and inter-satellite communications. Simulations of 1 Gbps data transmission through FSO links in both terrestrial and inter-satellite communications have been investigated to highlight potential atmospheric challenges in FSO.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Realization of free space optics with OFDM under atmospheric turbulence

Optik, Volume 125, Issue 18, Pages 5196–5198, Sep 2014

Free space optics (FSO) technology provides a promising solution for future broadband networks, o... more Free space optics (FSO) technology provides a promising solution for future broadband networks, offering high data transmission compared to RF technology. This work is focused on investigating the performance of an FSO system with OFDM and QAM. A 10 Gbps data stream is transmitted using a 4-level QAM sequence through the FSO system under different atmospheric conditions. Results indicate that the integration of SOA prolongs the maximum achievable distance with acceptable SNR to 185 km under clear weather conditions whereas under atmospheric fog, the maximum distance is extended to 2.5 km

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Research paper thumbnail of Selective Mode Excitation in SCM-OCDMA

International Conference on Photonics (ICP2013), Oct 2013

A six-channel 2.4GHz subcarrier multiplexing - optical code division multiple access (SCM-OCDMA) ... more A six-channel 2.4GHz subcarrier multiplexing - optical code division multiple access (SCM-OCDMA) system in conjunction with the selective excitation of LP01 and LP02 modes is presented for a multimode fiber Local Area Network. Simulation results demonstrate that mode selectivity increases the bandwidth-distance product and improves the BER performance of the channel.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Stepping Stone Perspective to Detection of Network Threats

International Journal of Applied Mathematics and Informatics, , Issue 3, Vol. 7, pp. 97 – 106, Oct 1, 2013

Current computing trends such as cloud computing, file sharing and social networking promote co... more Current computing trends such as cloud computing,
file sharing and social networking promote collaboration and allow greater mobility for users. Nevertheless, these computing trends increase the vulnerability of networks to security threats and challenge network resources. An ingenious technique employed by attackers for retaining anonymity is by exploiting intermediary host computers or stepping stones to instigate attacks on other computers. This paper explores novel application of the stepping stone detection concept in addressing network threats such as spams, backdoors, proxy server intrusions and denial of service attacks. Preliminary stepping stone detection models for each security threat will be constructed and the potential detection process is delineated. These preliminary concepts and models may prove useful for further optimization of network security in conjunction with other conventional detection techniques.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Fitness Value Based Evolution Algorithm Approach for Text Steganalysis Model

International Journal of Mathematical Models and Methods in Applied Sciences, May 2013

In this paper, we present a new alternative method for text steganalysis based on an evolution al... more In this paper, we present a new alternative method for text steganalysis based on an evolution algorithm, implemented using the Java Evolution Algorithms Package (JEAP).The main objective of this paper is to detect the existence of hidden messages ased on fitness values of a text description.It is found that the detection performance has been influenced by two groups of fitness values which are good fitness value and bad fitness value. This paper provides a valuable insight into the development and enhancement of the text steganalysis domain.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Performance Studies of Integrated Network Scenarios in a Hospital Environment

International Journal of Information Communication Technologies and Human Development (IJICTHD), Jun 2014

Hospital network is evolving towards a more integrated approach by interconnecting wireless techn... more Hospital network is evolving towards a more integrated approach by interconnecting wireless technologies into backbone networks. Although various integrated network scenarios have been published in the networking literature, a generic hospital model has not yet been fully explored and it remains a challenging topic in practice. One of the problems encountered by network practitioners is the seamless integration of network components into healthcare delivery. A good understanding of the performance of integrated networks is required for efficient design and deployment of such technologies in hospital environments. This research paper discuss on the modelling and evaluation of integrated network scenarios in hospital environments. The impact of traffic types (e.g. data, voice and video), traffic load, network size and signal strength on network performance is investigated by simulation. Three piloted case studies look at client performance in radiology Accident and Emergency (A & E and Intensive Care Unit (ICU)) scenarios. Each scenario reflects the need for various traffic types that end up distinct network behaviours. In the radiology scenario, email and File Transfer Protocol (FTP) traffic is found to perform well for medium-to-large networks. In the A & E scenario, Voice over Internet Protocol (VoIP) traffic is shown to generate very limited jitter and data loss. The performance is aligned with the Quality of Service (QoS) requirements. In the ICU scenario, the performance of video conference degrades with network size, thus, a QoS-enabled device is recommended to reduce the packet delay and data loss. IEEE 802.11a suits in hospital environment because it mitigates interference on the 2.4GHz band where most wireless devices operate.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Hospital Environment Scenarios using WLAN over OPNET Simulation Tool

International Journal of Information Communication Technologies and Human Development (IJICTHD), Jun 2014

For the past ten years, heterogeneous networks wired and wireless had tended to integrate seamles... more For the past ten years, heterogeneous networks wired and wireless had tended to integrate seamlessly, offering
effective and reliable service for medical operations. One of the problems encountered by network practitioners is the seamless integration of network components into healthcare delivery. As a multiplexing hospital model, the implementation certainly presents some challenges. The major technical and performance issues involve are as following. The operating parameters should keep aligned to the Quality of Service (QoS) requirement throughout simulation. Bandwidth utilisation of wireless networking is a challenging issue for real-time multimedia transmission. IEEE 802.11 provides relatively lower data rate than wired networks, thus the developer tends to adopt a more compromised solution: either reduce the file size or compress the image packets. Communication performance that varies constantly with the impact of signal strength, traffic load and interference. As stated radio signal senses as a curve and attenuates greatly while metallic object and
microwave exist within the active range. To ensure devices do not interfere with other electronic equipments (e.g. heart monitors), assert wireless spectrum has to be managed appropriately. This research paper aims to develop a generic hospital network scenarios using Wireless Local Area Network (WLAN) over OPNET Simulation, to evaluate the performance of the integrated network scenario for Intensive Care Units (ICU). This research makes use of computer simulation and discusses various aspects of the network design, so as to discover the performance behaviour pertaining to effect of traffic type, traffic load and network size. In the ICU scenario, the performance of video conference degrades with network size, thus, a QoS-enabled device is recommended to reduce the packet delay and data loss. IEEE 802.11a suits in hospital environment because it mitigates interference on the 2.4GHz band where most wireless devices operate. Experiment examines the effect of signal strength in WLAN. It is convinced that -88dBm is the best signal strength threshold. Although 802.11a generates slightly lower throughput than 802.11g, this issues can be addressed by placing more APs in the service area. It is convinced that 802.11a suits the hospital environments, because it mitigates interference on the popular 2.4GHz band where most wireless devices operate. It is important for medical devices which require future upgrade and Bluetooth deployment.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Anonymity Handling and Sensor Object Modeling for Pervasive Environments using VISA Processing

International Journal of Information Technology & Computer Science, Volume 15 Issue No 1, Jun 2014

Pervasive computing devices are configured for anywhere at any time services to adapt the changes... more Pervasive computing devices are configured for anywhere at any time services to adapt the changes in the dynamic
environment with respect to the user mobility. The paper proposes a salient model for a log based anonymity handling
in pervasive networks. The model defines a resource registry and sensor object modeling. Associability between the
nodes are configured with an allied user interface in the environment. Resource registry refers to a record of
information about the sensor nodes. A log book is maintained to keep track of the service discovery issues. New device
enquiry, registration and adaption are major issues in such pervasive devices. These issues lead to unacknowledged
communication that causes anonymity. This paper defines and discusses the presence of anonymity in pervasive
environments due to aforementioned issues.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Enhanced Probability Density Function Using APD in SAC-OCDMA Systems Based SPD Technique

2013 IEEE Symposium on Industrial Electronics and Applications (ISIEA 2013), Sep 22, 2013

This paper examines the avalanche photodiode (APD) gain impact on spectral-amplitude coding optic... more This paper examines the avalanche photodiode (APD) gain impact on spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems based single photodiode detection (SPD) technique. Numerical results are used for inspecting the APD gain influence upon the probability density function (PDF) and signal-to-noise ratio (SNR) performance. The usage of APD over positive-intrinsic-negative (PIN) photodiode accommodates more users with improved PDF and higher SNR.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Selective excitation of LP01 mode in multimode fiber using solid-core photonic crystal fiber

Journal of Modern Optics, Impact factor 1.166, Volume 60, Issue 20,pp. 1675-1683, Dec 2013

To address the overwhelming bandwidth increase in premise backbones, an attractive alternative fo... more To address the overwhelming bandwidth increase in premise backbones, an attractive alternative for selective mode excitation in multimode fiber (MMF) using solid-core photonic crystal fiber (PCF) is presented. The power coupling efficiency, differential mode delay, and bit-error rate performance of several structural designs of solid-core PCF waveguides are investigated for the selective excitation of mode LP01 in a MMF. The achieved coupling efficiency into mode LP01 is above 90% for PCF profiles with seven rings.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Comparison of single mode fiber and multimode fiber in deployment of SCM-OCDMA in Local Area Network

Key Engineering Materials, Advanced Materials Engineering and Technology II, Advanced Material Engineering & Technology, vol. 594-595, pp. 1037, Jan 2014

The integration of heterogeneous technologies promotes ubiquity and mobility. Optical code divisi... more The integration of heterogeneous technologies promotes ubiquity and mobility. Optical code division multiple access (OCDMA) may be deployed in conjunction to SCM to improve the spectral efficiency and enhance the data rate of subscribers in a Local Area Network (LAN). This paper compares the performance of multimode fiber to single mode fiber in the deployment of a SCM-OCDMA system with multi-diagonal (MD) codes in a LAN.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Tiering effect of solid-core photonic crystal fiber on controlled coupling into multimode fiber

Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications VII, Shizhuo Yin; Ruyan Guo, Editors, Proceedings of SPIE Vol. 8847 (SPIE, Bellingham, WA 2013), 88470Y., Sep 25, 2013

To address the overwhelming bandwidth increase in premise backbones, an attractive alternative fo... more To address the overwhelming bandwidth increase in premise backbones, an attractive alternative for selective mode excitation in multimode fiber (MMF) using solid-core photonic crystal fiber (PCF) is presented. The power coupling efficiency, differential mode delay and bit-error rate performance of several structural designs of solid-core PCF waveguides are investigated for the selective excitation of mode LP01 in a MMF. The achieved coupling efficiency into mode LP01 is above 90% for PCF profiles with seven rings.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of APD Gain Effect on SAC-OCDMA System using Modified-AND Detection Technique

Journal of Theoretical and Applied Information Technology, Vol. 53 Iss. 3, pp. 467-471, E-ISSN 1817-3195 / ISSN 1992-8645 , Jul 31, 2013

This paper investigates the avalanche photodiode (APD) gain effect on spectral-amplitude coding o... more This paper investigates the avalanche photodiode (APD) gain effect on spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) system using a modified-AND subtraction detection in comparison to the conventional AND detection scheme. Analytical results are presented to investigate the APD gain impact on the bit-error rate (BER) performance. In addition, we confirm the influence of the APD over the positive-intrinsic-negative (PIN) photodiode on the system performance using data transmission simulations.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Phase-Induced Intensity Noise Reduction with Improved Group Velocity Dispersion Tolerance in SAC-OCDMA Systems

International Journal of Engineering and Technology (IJET), Vol. 5 No. 1, pp. 95 - 100, Mar 2013

The demand for efficient optical communication systems has fuelled considerable research in devel... more The demand for efficient optical communication systems has fuelled considerable research in developing techniques for eradicating phase-induced intensity noise (PIIN) in spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA). This paper investigates the use of modified-AND subtraction detection technique to mitigate PIIN in SAC-OCDMA systems. The simulation results show that the modified-AND subtraction detection demonstrates better performance over the conventional AND detection approach. Furthermore, we have found that, from a transmission length of 40 km onwards, group velocity dispersion (GVD) degrades SAC-OCDMA system performance apparently. Dispersion compensating fiber (DCF) is used to lessen the influence of GVD caused by single mode fiber (SMF).

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Reducing BER of spectral-amplitude coding optical code-division multiple-access systems by single photodiode detection technique

Journal of European Optical Society. Rapid Publications, Vol. 8, 13022, Imp. Fac. 1.02, Mar 2013

In this paper, we present a single photodiode detection (SPD) technique for spectral-amplitude co... more In this paper, we present a single photodiode detection (SPD) technique for spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. The proposed technique eliminates both phase-induced intensity noise (PIIN) and multiple-access interference (MAI) in the optical domain. Analytical results show that for 35 simultaneous users transmitting at data rate of 622 Mbps, the bit-error rate (BER) = 1.4x10^-28 for SPD technique is much better compared to 9.3x10^-6 and 9.6x10^-3 for the modified-AND as well as the AND detection techniques, respectively. Moreover, we verified the improved performance afforded by the proposed technique using data transmission simulations

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Research paper thumbnail of Improving spectral efficiency of SAC-OCDMA systems by SPD scheme

This letter presents a single photodiode detection (SPD) as an effective technique for eradicatin... more This letter presents a single photodiode detection (SPD) as an effective technique for eradicating both multiple-access interference (MAI) and phase-induced intensity noise (PIIN) in spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. Mathematical analysis and simulation experiments are used to investigate the spectral efficiency (SE) of SAC-OCDMA systems utilizing different detection techniques. Results show that the SPD technique significantly enhances the SE compared to AND as well as modified-AND subtraction detections.

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Research paper thumbnail of Optimization of free space optics parameters: An optimum solution for bad weather conditions

Optik, Mar 2013

Free Space Optics Systems (FSO) is one of the most effective solutions, especially for atmospheri... more Free Space Optics Systems (FSO) is one of the most effective solutions, especially for atmospheric turbulence due to the weather and environment structure. Free space optics system suffers from various limitations. A well-known disadvantage of FSO is its sensitivity on local weather conditions-primarily to haze and rain, resulting in substantial loss of optical signal power over the communication path. The main objective of this article is to evaluate the quality of data transmission using Wavelength Division Multiplexing (WDM) with highlighting several factors that will affect the quality of data transmission. The results of these analyses are to develop a system of quality-free space optics for a high data rate transmission. From the result analysis, FSO wavelength with 1550 nm produces less effect in atmospheric attenuation. Short link range between the transmitter and receiver can optimize the FSO system transmission parameters or components. Based on the analysis, it is recommended to develop an FSO system of 2.5 Gbps with 1550 nm wavelength and link range up to 150 km at the clear weather condition of bit-error-rate (BER) 10−9

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Research paper thumbnail of Ultra Long Period Reversible Fiber Gratings as a Pressure Sensor

Advances in Computing, Communication and Control, Book Chapter, Springer, January 2013, pp. 439-443, , Jan 2013

We report here for the first time the fabrication and characterization of mechanically induced ul... more We report here for the first time the fabrication and characterization of mechanically induced ultralong period fiber gratings (MULPFG) with period size up to several millimeters. In these gratings the coupling of the fundamental guided core mode takes place with cladding modes of high diffraction orders.The transmission characteristic of grating with different external applied pressure has been experimentally verified.

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Research paper thumbnail of An Integrated Priority-Based Cell Attenuation Model for Dynamic Cell Sizing

A new, robust Integrated Priority-Based Cell Attenuation Model for dynamic cell sizing is propose... more A new, robust Integrated Priority-Based Cell Attenuation Model for dynamic cell sizing is proposed and simulated using real mobile traffic data. The proposed model is an integration of two main components; the Modified Virtual Community–Parallel Genetic Algorithm (VC-PGA) Cell Priority Selection Module and the Evolving Fuzzy (EFuNN) Mobile Traffic Prediction Module. The VC-PGA Module controls the number of cell attenuations by ordering the priority for the attenuation of all cells based on the level of mobile level of mobile traffic within each cell. The EFuNN Module predicts the traffic volume of a particular cell by extracting and inserting meaningful rules through incremental, supervised real-time learning. The EFuNN Module is placed in each cell and the output, the predicted mobile traffic volume of the particular cell, is sent to Local and Virtual Community Servers in the VC-PGA Module. The VC-PGA Module then assigns priorities for the size attenuation of all cells within the network, based on the predicted mobile traffic levels from the EFuNN Module at each cell. The performance of the proposed Module was evaluated on five adjacent cells in Selangor, Malaysia. Real-time predicted mobile traffic from the EFuNN structure was used to control the size of all the cells. Results obtained demonstrate the robustness of the Integrated Module in recognizing the temporal pattern of the mobile traffic and dynamically controlling the cell size in order to reduce the number of calls dropped.

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Research paper thumbnail of Optical Vortices In Wavelength Division Multiplexed Passive Optical Networks

Wavelength division multiplexing passive optical network (WDM –PON) is being widely considered fo... more Wavelength division multiplexing passive optical network (WDM –PON) is being widely considered for the deployment of fiber-to-the-home (FTTH) to deliver broadband access to business and home users. Optical vortices are helical wavefronts which focus to rings, rather than central points. This important property makes optical vortices ideal for exciting higher-order modes which are less prone to manufacturing defects in core refractive index and have closer propagation times. This research presents the application of VCSEL arrays for the independent transmission of parallel data streams over optical vortices in multimode fiber to increase the degrees of freedom in a FTTH WDM-PON. VCSEL arrays are selected for multiplexing optical vortices in WDM-PONs as they are tunable, compact, individually addressable and inexpensive. This book presents the mathematical framework and simulation of a novel design for WDM-PON using optical vortices. A transmission speed of 40Gbps is achieved at a central wavelength of 1550.12 nm while maintaining a BER of less than 1 x 10-9. The analysis reveals important results to be considered by operators towards the successful deployment of WDM-PON FTTH networks.

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Research paper thumbnail of Dynamic Cell Sizing in Mobile Cellular Networks: A framework for prioritization of cell attenuation

he proliferation of multimedia data services has spurred the remarkable growth of the mobile cell... more he proliferation of multimedia data services has spurred the remarkable growth of the mobile cellular network industry. To optimize the resources and performance of mobile cellular networks, spectrum management and traffic congestion control are key issues. In large cities, traffic demands are heavier in the city center compared to the suburbs, with a large busiest to quietest traffic ratio. Dynamic cell sizing is a flexible traffic congestion control mechanism which increases the capacity of a network by adaptively varying the pilot power to modify the coverage areas of cells for optimum performance under various traffic conditions. In order to mitigate the occurrence of coverage holes in a dynamic cell sizing environment, it is important to prioritize cell attenuation based on the traffic load of adjacent cells. This book presents a novel framework for predictive priority-based cell attenuation in dynamic cell sizing.

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Research paper thumbnail of VoIP over WLANs: An Efficient Scheduler to Support VoIP Traffic

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Research paper thumbnail of Discrete Structures: Lesson Plans And Reflections

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Research paper thumbnail of International Academic Award by Deputy Prime Minister of Malaysia, February 2013

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Research paper thumbnail of Fulbright Award, September 2013

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Research paper thumbnail of Highest Recipient, “Journal Publication Incentive Award”, Publication, Research and Innovation Ceremony, 26th June 2012

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Research paper thumbnail of Excellent Performance for Year 2011

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Research paper thumbnail of Teaching Certification (Excellent), 2012

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Research paper thumbnail of DAAD Award, 2005

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Research paper thumbnail of Editor, International Journal of Informatics and Communication Technology (IJ-ICT)

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Research paper thumbnail of Editor, International Journal of Electrical and Computer Engineering (IJECE)

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Research paper thumbnail of Reviewer, Optics Express, Impact Factor 3.75

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Research paper thumbnail of Reviewer, Journal of Lightwave Technology Journal, Impact Factor 2.26

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Research paper thumbnail of Reviewer, Optics Letters, Impact Factor 3.2

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Research paper thumbnail of Reviewer, Journal of Modern Optics, Impact Factor 1.17

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Research paper thumbnail of Editor, International Journal of Electrical and Computer Engineering

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Research paper thumbnail of Editor, International Journal of Informatics and Communication Technology

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Research paper thumbnail of Bandwidth Enhancement Techniques in Multimode Fibre (Invited)

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Research paper thumbnail of Holographic Selective Mode Excitation in Multimode Fibre (Invited

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Research paper thumbnail of Holographic Selective Mode Excitation in Multimode Fibre

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Research paper thumbnail of Holographic Transceiver for a Multimode Waveguide

An optical transceiver using a transmissive binary amplitude spatial light modulator and three le... more An optical transceiver using a transmissive binary amplitude spatial light modulator and three lenses is proposed for enhancing the bandwidth of a multimode fiber channel. Theoretical modal electric field information is provided to optimize the channel impulse response, thereby reducing the number of iterations required for reducing modal dispersion and increasing the bandwidth. The proposed holographic transceiver increases the bandwidth of a conventional launch, particularly for local area network systems. The increased transmission speed and link capacity supports ubiquitous multimedia-rich applications in business, education, medicine and media industries.

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Research paper thumbnail of Massachusetts Institute of Technology, Cambridge, USA, 2013 - 2014

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Research paper thumbnail of University of Oxford, 2005 - 2009

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Research paper thumbnail of Technische Universität Braunschweig, 2005

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Research paper thumbnail of Optical Fiber Communications, John Senior

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Research paper thumbnail of An Introduction to Optical Waveguides, M. J. Adams

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Research paper thumbnail of Digital Communications, John Proakis

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Research paper thumbnail of Introduction to Fourier Optics, Joseph Goodman

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Research paper thumbnail of Optics, Eugene Hecht

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Research paper thumbnail of Fundamentals of Applied Electromagnetics, Fawwaz T. Ulaby

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Research paper thumbnail of Optical Waveguide Theory, Allan W. Snyder, John Love

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Research paper thumbnail of Advanced Engineering Electromagnetics, Constantine A. Balanis

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Research paper thumbnail of Essentials of Computational Electromagnetics, Xin-Qing Sheng

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Research paper thumbnail of Numerical Methods for Engineering, Karl F. Warnick

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Research paper thumbnail of Proposed new approach to the design of universal logic gates using the electro-optic effect in Mach–Zehnder interferometers

Applied Optics, 2015

Efficient application of the electro-optic effect in a lithium-niobate-based Mach-Zehnder interfe... more Efficient application of the electro-optic effect in a lithium-niobate-based Mach-Zehnder interferometer to construct universal gates has been demonstrated. The study is carried out by simulating the proposed device with the beam propagation method, and the results are verified using MATLAB. Various parameters influencing the performance of the device (such as speed, latency, and power consumption) also have been taken into account.

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Research paper thumbnail of Design of 1-bit and 2-bit magnitude comparators using electro-optic effect in Mach–Zehnder interferometers

Optics Communications, 2015

The Mach–Zehnder interferometer (MZI) structures collectively show powerful capability in switchi... more The Mach–Zehnder interferometer (MZI) structures collectively show powerful capability in switching an input optical signal to a desired output port from a collection of output ports. Hence, it is possible to construct complex optical combinational digital circuits using the electro-optic effect constituting MZI structure as a basic building block. Optical switches have been designed for 1-bit and 2-bit magnitude comparators based on electro-optic effect using Mach–Zehnder interferometers. The paper constitutes a mathematical description of the proposed device and thereafter simulation using MATLAB. Analysis of some factors influencing the performances of proposed device has been discussed properly. The study is verified using beam propagation method.

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Research paper thumbnail of Implementation of 2-bit multiplier based on electro-optic effect in Mach–Zehnder interferometers

Optical and Quantum Electronics, 2015

The optical switching phenomena have been studied and their efficient applications to construct t... more The optical switching phenomena have been studied and their efficient applications to construct the 2-bit multiplier based on electro-optic effect in Mach-Zehnder interferometers (MZIs) have been used. The Mach–Zehnder interferometer (MZI) structures working on the principle of electro-optic effect show the powerful ability to switch the optical signal from one output port to the other output port. Hence, it is possible to construct some complex optical combinational digital circuits using the electro-optic effect based MZI structure as a basic building block. The paper constitutes the mathematical description of proposed device and thereafter compilation using MATLAB. The study is carried out by simulating the proposed device with Beam propagation method (BPM).

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Research paper thumbnail of Design of photonics crystal fiber sensors for bio-medical applications

Optical Measurement Systems for Industrial Inspection IX, 2015

ABSTRACT Photonic Crystal Fibers (PCFs) have special structures and offer a number of novel desig... more ABSTRACT Photonic Crystal Fibers (PCFs) have special structures and offer a number of novel design options, such as very large or very small mode areas, high numerical aperture, guidance of light in air, and novel dispersion properties. PCFs have become an attractive field for the researchers and they are trying to work on these to get their properties applied in dispersion related applications, sensing applications and much more. PCFs sensors are widely used in bio-medical applications. The sensitivity and performance of sensors are enhanced due to novel applications of PCFs. This paper outlines a novel design for a generalized biomedical sensor by collaborating PCF and electro-optic effect of Lithium Niobate (LiNbO_3) based Mach-Zehnder interferometer (MZI) structure.

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Research paper thumbnail of Radio Subcarrier Spacing Effect on SCM-MDM Using HG Modes in Radio-Over-Fiber

Advanced Science Letters, 2015

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Research paper thumbnail of Design of parity generator and checker circuit using electro-optic effect of Mach–Zehnder interferometers

Optics Communications, 2016

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Research paper thumbnail of Improvement in Temperature Sensitivity of FBG by Coating of Different Materials

Optik - International Journal for Light and Electron Optics, 2015

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Research paper thumbnail of Optical Universal Logic Gates based on Electro-Optic Effect of Lithium Niobate in Mach-Zehnder Interferometer

Frontiers in Optics 2015, 2015

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Research paper thumbnail of Implementation of Sequence Generator using Electro-Optic Effect of Mach-Zehnder Interferomete

Frontiers in Optics 2015, 2015

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Research paper thumbnail of Optical Bit Pattern Recognition System for Optical Network Applications

Frontiers in Optics 2015, 2015

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Research paper thumbnail of 5Gbps HG 0,1 and HG 0,3 optical mode division multiplexing for RoFSO

2015 IEEE 11th International Colloquium on Signal Processing & Its Applications (CSPA), 2015

Radio-over-free-space optics (Ro-FSO) technology harnesses the large capacity of optical fiber an... more Radio-over-free-space optics (Ro-FSO) technology harnesses the large capacity of optical fiber and the mobility native to wireless networks. To increase the capacity of Ro-FSO networks, this work introduces a new optical mode division multiplexing (MDM) scheme for Ro-FSO by incorporating optical Hermite-Gaussian modes HG 0, 1 and HG 0, 3 for transmitting two distinct 2.5 Gbps data modulated on 10 GHz radio subcarriers. Signal-to-noise ratios and bit-error-rates show successful 2 x 2.5Gbps data transmission of 10GHz radio-modulated subcarriers over the two HG optical carriers through a 800m free-space channel.

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Research paper thumbnail of An Integrated Model for Cell Attenuation in Dynamic Cell Sizing

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Research paper thumbnail of A Cell Attenuation Model in Dynamic Cell Sizing

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Research paper thumbnail of Free-Space Optical Mode Divisison Multiplexing for Switching Between Millimeter-Wave Picocells

This work introduces a new optical Hermite-Gaussian mode division multiplexing scheme for switchi... more This work introduces a new optical Hermite-Gaussian mode division multiplexing scheme for switching between different picocells in a Ro-FSO network using a spatial correlator. Distinct 2.5GHz 10GHz radio-modulated subcarrier data streams from two picocells over disparate 850nm optical Hermite-Gaussian mode carriers were successfully switched to two different picocells separated by 1km by means of spatial correlation and modal decomposition of optical Hermite-Gaussian modes into linearly polarized modes. Optical signal-to-noise ratios, bit-error-rates and modal decomposition results demonstrate effective data transmission between the picocells

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Research paper thumbnail of Mode division multiplexing of spiral-phased donut modes in multimode fiber

International Conference on Optical and Photonic Engineering (icOPEN 2015), 2015

ABSTRACT In the advent of tremendous data growth in local area networks, various dimensions for m... more ABSTRACT In the advent of tremendous data growth in local area networks, various dimensions for multiplexing and modulating data in multimode fiber have been utilized in the intensity, phase, wavelength and time domains. The modal dimension, however, has been relatively untapped. This paper models mode division multiplexing (MDM) of spiral-phased donut modes of different diameters generated from two VCSEL arrays and coupled into a MMF. A data rate of 40Gb/s for a distance of 1500 meters is achieved. The power coupling coefficients, modal delays and bit-error rates at the photodetectors are analyzed for different mode vortex orders.

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Research paper thumbnail of Roshidi NAUN FitnessValue

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Research paper thumbnail of Free-space optical mode division multiplexing for switching between millimeter-wave picocells

International Conference on Optical and Photonic Engineering (icOPEN 2015), 2015

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Research paper thumbnail of 5 × 5 25 Gbit/s WDM-MDM

Journal of Optical Communications, 2015

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Research paper thumbnail of Secure MDM-OFDM-Ro-FSO System Using HG Modes

International Journal of Sensors Wireless Communications and Control, 2015

Radio-over-free-space-optics (Ro-FSO) is a promising technique to distribute radio frequency (RF)... more Radio-over-free-space-optics (Ro-FSO) is a promising technique to distribute radio frequency (RF) signals over the atmosphere using optical carriers. In this work, we designed a 60Gbps-120GHz OFDM-Ro-FSO transmission system in conjunction with mode division multiplexing. Three independent 40 GHz radio signal are optically modulated at 20 Gbps and transported over a secure free-space link of 50 km by mode division multiplexing of three Hermite-Guassian modes HG 00, HG 01 and HG 02.

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Research paper thumbnail of Design of D flip-flop and T flip-flop using Mach–Zehnder interferometers for high-speed communication

Applied Optics (OSA), Jul 14, 2015

Electrical component speed is a major constraint in high-speed communications. To overcome this c... more Electrical component speed is a major constraint in high-speed communications. To overcome this constraint,
electrical components are now being replaced by optical components. The application of optical switching
phenomena has been used to construct the design of the D flip-flop and T flip-flop based on the electro-optic
effect in a Mach–Zehnder interferometer (MZI). The MZI structures show the powerful ability to switch the
optical signal from one output port to the other. Hence, it is possible to construct some complex optical combinational digital circuits using the electro-optic-effect-based MZI structure as a basic building block. This paper
constitutes the mathematical description of the proposed device and thereafter compilation using MATLAB.
The study is carried out by simulating the proposed device with the beam propagation method.

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