Browsing by Author "Thilakumara, R. P"

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    PublicationOpen Access
    Low Cost Optical Power Meter and Bandwidth Analyser with Wide Dynamic Range
    (researchgate.net, 2014-12-16) Samarawickrama, Y. C; Thilakumara, R. P
    Fiber optic communication is a booming technology in the field of telecommunication due to the advantages over traditional communication systems. It is a timely requirement to produce optical equipment at low cost and reasonable measurement accuracy. This research is about designing of an optical power meter and analyser that can be used in laboratories for educational experimental purposes and for optical signal power measurements to troubleshoot connectivity of optical links. Analyser measures the bandwidth of a modulated optical signal up to 500MHz.Both power meter and analyser can be used for 850nm, 1310nm and 1550nm optical wavelengths. Photodiodes, Logarithmic conversion amplifiers, Trans impedance amplifiers are the main components used in the design. Integrated power meter and analyser, low cost, reasonable measurement accuracy and data logging capability are outstanding features.
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    PublicationEmbargo
    Multiuser Access in LiFi using OFDMA
    (IEEE, 2018-10-27) Wijesinghe, S. S; Thilakumara, R. P
    Light Fidelity (LiFi) is an emerging optical technology for wireless data access in short range communication to complement WiFi, a well-established radio frequency (RF) wireless indoor communication standard. Electromagnetic Pollution, relatively low data bandwidths, multipath interference of the indoor propagation to degrade performance, vulnerability to eavesdropping and susceptibility to security threats are major factors that favors LiFi in place of WiFi. However LiFi being an optical technology imposes great difficulty in implementing multiuser access in the Uplink from the user to router. Using Wavelength Division Multiplexing (WDM) for multiuser access drastically increases the cost and complexity of transceivers. This work presents a novel technique of multiuser access using Orthogonal Frequency Division Multiplexing (OFDM) with single carrier per user, implemented by envelope modulation of optical subcarriers for spatially separated users providing compatibility in uplink and downlink of LiFi standard based on OFDM.
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    PublicationEmbargo
    Optical character recognition for Sinhala language
    (IEEE, 2013-08-23) Rimas, M; Thilakumara, R. P; Koswatta, P
    A rotationally invariant optical character recognition system for Sinhala language is developed using Two Dimensional Fourier Transform and Artificial Neural Networks. Sinhala characters of different fonts and font sizes are recognized with over 85% recognition accuracy. Segmentation method based on histogram used in this system gives segmentation accuracy over 70% for complex Sinhala characters.
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    PublicationEmbargo
    PAPR Reduction and Multiuser Access using OFDMA for LiFi
    (IEEE, 2020-01-10) Wijesinghe, S. S; Thilakumara, R. P
    Light Fidelity (LiFi) is a novel optical communication technology used in indoor short range wireless communication, competing Radio Frequency (RF) WiFi technology. This technology increases the transmission capacity in indoor propagation while eliminating unwanted Electromagnetic pollution, multipath interference and security threats in RF technology.While OFDMA in LiFi guarantees a more reliable and flexible communication, the peak to average power ratio (PAPR) could impose practical difficulty in designing LiFi OFDM receivers when more subcarriers are added to form the composite OFDM signal due to the need of a larger dynamic range for the receiver. This work presents a novel PWM (Pulse Width Modulated) OFDM approach for Free Space Optical Communication (FSOC) systems that resolves the PAPR problem while providing multiuser access in the uplink from spatially separated users. The energy of the OFDM signal is translated from vertical to horizontal representation using PWM to reduce PAPR problem. This technique can also removes additive noise in propagation by limiting the signal amplitude at the receiver to increase the robustness to noise. This novel method has the potential for very high data rates in short range wireless optical links while providing multiuser wireless access from spatially separate locations.
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    PublicationEmbargo
    Plant recognition system based on Neural Networks
    (IEEE, 2013-01-23) Rankothge, W. H; Dissanayake, D. M. S. B; Gunathilaka, U. V. K. T; Gunarathna, S. A. C. M; Mudalige, C. M; Thilakumara, R. P
    With the evolution of technologies, people have adopted their day today lives to utilize the benefits of highly advanced technologies. Artificial Intelligence and Neural Networks are playing major roles in this process and they have been involved in fields of medicine, automobiles, aeronautical science, military and many more. Unfortunately very little concern is devoted to the botanical science field, especially in taxonomic researches of plants. Even today, identification and classification of unknown plant species are performed manually by expert personnel who are very few in number. It takes a long time and the results are not very accurate. Advanced Plant Identification System (APIS) is an intelligent system which has the ability to identify tree species from photographs of their leaves and it provides more accurate results within less time.