Ahmad Dhaini
American University of Beirut, Computer Science, Faculty Member
- Dr. Ahmad R. Dhaini is an Assistant Professor of Computer Science at the American University of Beirut (AUB). He rece... moreDr. Ahmad R. Dhaini is an Assistant Professor of Computer Science at the American University of Beirut (AUB).
He received his B.Sc. in Computer Science from AUB in 2004. He then earned his M.Sc. degree in Electrical and Computer Engineering from Concordia University, Montreal, Canada in 2006. His Master’s dissertation was nominated for the best thesis award. In 2006-2007, he worked as a Software Analyst and Consultant at TEKSystems, Montreal, Canada; and in 2007-2008, as a Software Designer at Ericsson, Montreal, Canada. He completed his Ph.D. degree in Electrical and Computer Engineering from University of Waterloo, Canada in 3 years only (2008-2011), and was granted several awards such as the Ontario Graduate Scholarship in Science and Technology (OGSST), and other various teaching and research awards at University of Waterloo. In 2011-2012, he worked as a Research Associate at University of Waterloo, Canada, and as a Consultant at KAUST, Saudi Arabia.
In 2012-2014, Dr. Dhaini was a Postdoctoral Scholar at Stanford University, working in the Photonics and Networking Research Laboratory (PNRL) lead by Prof. Leonid Kazovsky (known as the father of optical coherent transmission), after being awarded the prestigious Natural Sciences and Engineering Research Council of Canada Postdoctoral Fellowship (NSERC PDF). He also completed the Stanford Ignite program for entrepreneurship and innovation; it is a mini-MBA program in Stanford’s Graduate School of Business, designed to teach scientists how to convert an idea into a business.
Dr. Dhaini is an inventor with US patents. He has also authored/co-authored one book, one book chapter, and more than 40 highly cited research articles in top IEEE journals and conferences. He is a reviewer for NSF, NSERC, and several US universities’ internal grants. He also serves as Editor for Springer’s Photonics Networks Communications journal, and reviewer and technical program committee (TPC) member for several major IEEE journals and conferences.
His research interests cover several themes of optical networks such as fiber-wireless (FiWi) broadband access networks, mission-critical networks, green communications, and software-defined networking. He has been also tackling research problems related to Biotechnology; more specifically in the areas of mobile health (mHealth) and medical image analysis.edit
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Research Interests: Computer Science, Distributed Computing, Broadband, Computer Network, Wireless Network, and 10 moreBroadband Networks, Quality of Service, Real Time Systems, Wimax, Resource Management, EPON, Wireless Broadband, IEEE Communications Magazine, Electrical And Electronic Engineering, and Private Network
Ethernet passive optical networks (EPONs) are being designed to deliver multiple services and applications, such as voice communications (VoIP), standard and high-definition video (STV and HDTV), video conferencing (interactive video) and... more
Ethernet passive optical networks (EPONs) are being designed to deliver multiple services and applications, such as voice communications (VoIP), standard and high-definition video (STV and HDTV), video conferencing (interactive video) and data traffic access network. However, most of the current work focuses on inter-ONU dynamic bandwidth allocation (DBA) algorithms. In this paper, we concentrate on the intra-ONU bandwidth allocation for
Research Interests: Computer Science, Video Conferencing, Videoconference, Computer Network, Interactive Video, and 9 moreBandwidth Allocation, Jitter, Dynamic Bandwidth Allocation, Simulation experiment, Dynamic Channel Allocation, High Definition, Ethernet Passive Optical Network, Access Network, and Weighted Round Robin
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Research Interests: Computer Science, Fiber Optics, Algorithm, Access Networks, Control system, and 15 moreComputer Network, Bandwidth Allocation, Bandwidth management, Dynamic Bandwidth Allocation, High Resolution, Availability, Dynamic Channel Allocation, Bandwidth, High Definition, Admission Control, Electrical And Electronic Engineering, Ethernet Passive Optical Network, Access Network, Channel Allocation, and Differentiated Services
Cloud computing has been the killer technology for offering dynamically scalable infrastructure to modern Internet applications. However, cloud networks can be a burden for latency-sensitive applications such as Tactile Internet, which... more
Cloud computing has been the killer technology for offering dynamically scalable infrastructure to modern Internet applications. However, cloud networks can be a burden for latency-sensitive applications such as Tactile Internet, which can't afford the high delay due to communication with remote cloud servers. In this paper, we exploit content distribution networks deployed by Internet service providers, and next-generation passive optical networks to construct agile, programmable and scalable Optical CLoud Distribution Networks (OCLDN). With OCLDN, a software defined networking (SDN)-based mini-cloud data center is installed at the central office, which includes a cloud-based tactile steering server, and supports all types of cloud applications. To meet the stringent quality-of-service (QoS) requirements for new and existing services, we propose a new Dynamic Wavelength and Bandwidth Allocation scheme, which employs the Water-Filling technique and advanced intra- ONU scheduling. Extensive simulations are performed; results highlight the effectiveness of the proposed scheme in supporting the new types of services without impairing the QoS demands for new and legacy data services.
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Research Interests: Engineering, Medical Imaging, Fiber Optics, Next Generation Networks, Broadband, and 15 moreComputer Network, Broadband Networks, Optical, Light, Local Area Networks, Multiplexing, Network Capacity, Analytical Model, Next Generation, Broadband Access, Admission Control, Electrical And Electronic Engineering, Ethernet Passive Optical Network, Access Network, and FREQUENCY DIVISION MULTIPLEXING
Research and development on optical networks generally and on Passive Optical Networks (PON) particularly have matured considerably. The exponential increase in the demand for bandwidth has exposed many challenges in the "last... more
Research and development on optical networks generally and on Passive Optical Networks (PON) particularly have matured considerably. The exponential increase in the demand for bandwidth has exposed many challenges in the "last mile" that remains the bottleneck in broadband access networks. Currently, Ethernet PON has emerged as the most inexpensive panacea, providing more bandwidth than Cable Modems and Digital Subscriber Lines. Nevertheless, providing fair and efficient Quality of Service (QoS) has always been a major issue due to the un-deterministic nature of Time Division Multiple Access (TDMA) technology and the limited 1 Gbps channel speed that EPON relies on; unlike backbone networks that uses the Wavelength Division Multiplexing (WDM) technology. This book instruments these challenges and issues and offers effective solutions. More specifically, it presents an upgrade from a TDM-PON to a Hybrid TDM/WDM-PON and proposes and validates the first framework that enables for per-stream QoS protection in EPON using a new fair QoS scheduler. The book addresses professionals in optical and access networks. It is also directed towards researchers who would like to get a novel fragrance of EPONs.
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ABSTRACT Energy efficiency is rapidly becoming an important requirement for modern networks. In this paper, we discuss the physical limits to the power consumption of wireless and optical transmission. We show that there is an optimum... more
ABSTRACT Energy efficiency is rapidly becoming an important requirement for modern networks. In this paper, we discuss the physical limits to the power consumption of wireless and optical transmission. We show that there is an optimum cell size that results in the least power consumption in optical/wireless in-building networks and explain why. We then discuss the principles that govern the design of in-building Radio-over-Fiber (RoF) distribution networks. We use theoretical models to analyze the impact of key design factors on the energy consumption of point-to-point RoF links and how their adverse effects can be mitigated. Finally, we compare the energy consumption of several key in-building optical/wireless architectures based on several different RoF technologies, and demonstrate that centralized architectures based on RoF links can be substantially more energy efficient than baseband-over-fiber (BoF) architectures in network capacity-limited scenarios, when designed properly. Our findings also show that RoF-based architectures are energy efficient for cell sizes less than 10m.
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Radio-over-Fiber (RoF) based network architectures would allow centralization of signal processing and signal conditioning functions and simple, cost-effective remote units at the cell site. RoF technology results in remote units with few... more
Radio-over-Fiber (RoF) based network architectures would allow centralization of signal processing and signal conditioning functions and simple, cost-effective remote units at the cell site. RoF technology results in remote units with few components, however, certain aspects of the technology may inadvertently lead to high power consuming components. In this paper, we experimentally investigate the effect of electrical-optical-electrical (E/O/E) loss and signal bandwidth on the energy consumption of analog and digitized RoF (ARoF and DRoF) links. We also analyze the energy efficiency of multiple services on a single RoF distribution network. Our results show that E/O/E loss significantly degrades the energy efficiency of the ARoF links. DRoF is robust to the E/O/E loss on the optical link but is affected by the loss due to reconstruction of the radio frequency signal at higher Nyquist zones. We also show that increasing the bandwidth improves the energy efficiency. Finally, we demonstrate that the extra energy savings from having multiple services on a single RoF link depends on the wireless environment.
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Research Interests: Computer Science, Computer Network, Passive Optical Networks, Bandwidth Allocation, Multiplexing, and 13 moreEPON, Dynamic Bandwidth Allocation, Wavelength Division Multiplexing, Integrated Services, Simulation experiment, Exploit, Dynamic Channel Allocation, Bandwidth, Time Division Multiplexing, Ethernet Passive Optical Network, Intelligent Networks, Upgrade, and Access Network
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Research Interests: Computer Science, Distributed Computing, Next Generation Networks, Energy efficiency, Queuing Theory, and 9 moreBroadband, Computer Network, Passive Optical Networks, Bandwidth Allocation, TDMA (Time division multiple access), Dynamic Bandwidth Allocation, Quality of Service (QoS), Analytical Model, and Energy Efficiency
ABSTRACT UltraFlow - also known as Optical Flow Switching (OFS) has been recently presented as an effective technology for large Internet data transfer. In this paper, we propose a novel scheduling mechanism for the Stanford UltraFlow... more
ABSTRACT UltraFlow - also known as Optical Flow Switching (OFS) has been recently presented as an effective technology for large Internet data transfer. In this paper, we propose a novel scheduling mechanism for the Stanford UltraFlow access network, a novel optical access network architecture that offers dual-mode service to the end-users: legacy IP and OFS. The proposed scheme is a hybrid mechanism that combines the batch scheduling technique with existing methods so as to increase the average Flow throughput, while maintaining relatively low traffic latency. Extensive simulations highlight the advantages of the proposed solution and demonstrate its merits.
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The Book cover the research efforts made in the field of Passive Optical Access Networks in the recent years.Theory and principles of the related fields are presented with comprehension. Different Network Architectures of Downstream and... more
The Book cover the research efforts made in the field of Passive Optical Access Networks in the recent years.Theory and principles of the related fields are presented with comprehension. Different Network Architectures of Downstream and upstream for achieving colorless transmission in passive optical access networks are included. Performance of Passive Optical Networks are analyzed through simulation and experimental work. The Design issues of Transmitters and Receivers are addressed with detailed analysis .The analysis parameters mainly include data rate, launch power, transmission distance, Bet Error Rate and Signal to Noise Ratio. impact of Non linear factors like Rayleigh backscattering on the transmission performance is also presented. Power Budgeting issues of various scheme are also included in analysis part. The Results are presented pictorially with powerful tool of ORIGIN.The Conclusions are drawn and presented in effective way .
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Over the last decade, passive optical network (PON) has been taken as the most promising next-generation access network. To improve the energy efficiency in PON systems, the ITU-T standard for next-generation PON system introduced a new... more
Over the last decade, passive optical network (PON) has been taken as the most promising next-generation access network. To improve the energy efficiency in PON systems, the ITU-T standard for next-generation PON system introduced a new power management mode, so-called the Watchful Sleep mode. This new mode is expected to be operated on any TDM-PON or GPON variant. Although the sleep mechanism under the Watchful Sleep mode is well defined, its performance can vary greatly depending on the criteria used to start and/or terminate the power saving phase. In this article, we present a comprehensive analytical model for evaluating the energy efficiency of the watchful sleep mode using the Delayed Wakeup (DWU) mechanism. We then compare its performance with the Immediate Wakeup (IWU) scheme. Our analytical and simulation results highlight the accuracy of the presented model and prove its merits.
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Corneal cross-linking (CXL) is a surgical intervention to treat the progression of an eye disease called keratoconus that may lead to significant loss of visual acuity. Manually detecting the presence and the depth of a stromal... more
Corneal cross-linking (CXL) is a surgical intervention to treat the progression of an eye disease called keratoconus that may lead to significant loss of visual acuity. Manually detecting the presence and the depth of a stromal demarcation line in optical coherence tomography (OCT) images is a standard procedure used by ophthalmologists to check the success of CXL. In this paper, we propose a deep learning model trained in a semi-weakly supervised fashion to segment the area between the top boundary of the cornea and the demarcation line that is later used by our extraction algorithm to obtain the demarcation line automatically. We report an improvement in performance compared to the fully supervised learning approaches in terms of the dice coefficient.
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PURPOSE To evaluate and compare corneal haze as determined by optical coherence tomography (OCT) after corneal cross-linking (CXL) for the treatment of mild to moderate keratoconus with or without mitomycin C (MMC) application. METHODS... more
PURPOSE To evaluate and compare corneal haze as determined by optical coherence tomography (OCT) after corneal cross-linking (CXL) for the treatment of mild to moderate keratoconus with or without mitomycin C (MMC) application. METHODS This was a retrospective analysis of 87 eyes of 72 patients with mild to moderate keratoconus. The first group (n = 44 eyes) underwent CXL between June 2013 and January 2015 and the second group (n = 43 eyes) underwent CXL with MMC (CXL+MMC) between February and December 2015, both following the Dresden protocol. Patients were evaluated preoperatively and at 1, 3, 6, and 12 months postoperatively. Main outcome measures were corneal reflectivity and haze reflectivity measured by a specially developed OCT image analysis software. RESULTS Anterior corneal reflectivity at 1 month and 1 year postoperatively was 14.79 ± 4.68 and 25.97 ± 15.01 (P < .001), and 13.88 ± 4.39 and 18.41 ± 9.25 (P = .025) for the CXL and CXL+MMC groups, respectively. The reflectivity of the anterior stromal haze region at 1 month and 1 year postoperatively was 23.15 ± 5.91 and 33.14 ± 16.58 (P = .005), and 20.58 ± 7.88 and 27.14 ± 12.80 (P = .049) for both groups, respectively. The changes in simulated keratometry from preoperatively to postoperatively were similar in both groups. The CXL+MMC group showed larger maximum keratometry flattening: 53.41 ± 6.88 diopters (D) preoperatively and 49.44 ± 5.66 D 1 year postoperatively versus 52.27 ± 5.78 and 50.91 ± 4.25 D for CXL alone (P = .008). CONCLUSIONS MMC application following CXL significantly increases corneal haze. Similar studies need to be performed on simultaneous CXL and photorefractive keratectomy to evaluate the role of MMC in haze formation in such procedures. [J Refract Surg. 2021;37(2):83-90.].
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To evaluate a proposed technology for offering objective grading and mapping of corneal haze as detected by corneal spectral domain optical coherence tomography after corneal cross-linking. This was a retrospective study to evaluate... more
To evaluate a proposed technology for offering objective grading and mapping of corneal haze as detected by corneal spectral domain optical coherence tomography after corneal cross-linking. This was a retrospective study to evaluate corneal optical coherence tomography images performed on 44 eyes of 44 patients who underwent corneal cross-linking between January 2014 and May 2015, at the American University of Beirut Medical Center. Overall average brightness of the cornea was markedly increased from 43.4% (±6.0) at baseline to 50.2% (±4.4) at 1 month, 47.9% (±4.4) at 3 months, and 46.4% (±5.7) at 6 months with P <0.001, <0.001, and 0.005, respectively. In the anterior stroma, the average brightness significantly increased at 1, 3, and 6 months with values of 54.8% (±3.9), 52.5% (±5.2), and 49.7% (±6.9) with P <0.001, <0.001, and 0.003, respectively. In the mid stroma, the change was clinically significant at 1 and 3 months, whereas in the posterior stroma, it was only s...
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Ethernet Passive Optical Networks (EPONs) are considered the most promising solutions for upgrading the cur- rent congested access networks to enable the delivery of broad- band integrated services. Although current EPON architectures are... more
Ethernet Passive Optical Networks (EPONs) are considered the most promising solutions for upgrading the cur- rent congested access networks to enable the delivery of broad- band integrated services. Although current EPON architectures are economically feasible, they are however bandwidth limited. In this paper, we discuss a simple upgrade architecture from EPON to WDM-PON. We present various Dynamic Wavelength and Bandwidth
Research Interests: Computer Science, Computer Network, Passive Optical Networks, Bandwidth Allocation, Multiplexing, and 13 moreEPON, Dynamic Bandwidth Allocation, Wavelength Division Multiplexing, Integrated Services, Simulation experiment, Exploit, Dynamic Channel Allocation, Bandwidth, Time Division Multiplexing, Ethernet Passive Optical Network, Intelligent Networks, Upgrade, and Access Network
Research Interests: Engineering, Computer Science, Scheduling, Computer Network, Passive Optical Networks, and 15 moreLocal Area Networks, Bandwidth Allocation, Multiplexing, Cost effectiveness, Resource Management, EPON, Ethernet, Dynamic Bandwidth Allocation, Wavelength Division Multiplexing, Simulation experiment, Simulation and Modeling, Ethernet Passive Optical Network, Optical Cross-connect, Access Network, and Fiber to the home
Ethernet passive optical networks (EPONs) are being designed to deliver multiple services and applications, such as voice communications (VoIP), standard and high-definition video (STV and HDTV), video conferencing (interactive video) and... more
Ethernet passive optical networks (EPONs) are being designed to deliver multiple services and applications, such as voice communications (VoIP), standard and high-definition video (STV and HDTV), video conferencing (interactive video) and data traffic access network. However, most of the current work focuses on inter-ONU dynamic bandwidth allocation (DBA) algorithms. In this paper, we concentrate on the intra-ONU bandwidth allocation for
Research Interests: Computer Science, Video Conferencing, Videoconference, Computer Network, Interactive Video, and 9 moreBandwidth Allocation, Jitter, Dynamic Bandwidth Allocation, Simulation experiment, Dynamic Channel Allocation, High Definition, Ethernet Passive Optical Network, Access Network, and Weighted Round Robin
Page 1. Chapter 8 Quality of Service in Ethernet Passive Optical Networks (EPONs) Ahmad Dhaini and Chadi Assi Abstract Ethernet passive optical networks (EPONs) are designed to deliver mul-tiple services and applications ...
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Research Interests: Computer Science, Video Conferencing, Videoconference, Computer Network, Quality of Service, and 12 moreInteractive Video, Passive Optical Networks, Jitter, Dynamic Bandwidth Allocation, Wavelength Division Multiplexing, Simulation experiment, Bandwidth, Tunable Diode Laser, Time Division Multiplexing, Communications, Ethernet Passive Optical Network, and Access Network
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Research Interests: Computer Science, Fiber Optics, Algorithm, Access Networks, Control system, and 15 moreComputer Network, Bandwidth Allocation, Bandwidth management, Dynamic Bandwidth Allocation, High Resolution, Availability, Dynamic Channel Allocation, Bandwidth, High Definition, Admission Control, Electrical And Electronic Engineering, Ethernet Passive Optical Network, Access Network, Channel Allocation, and Differentiated Services
Research Interests: Engineering, Computer Science, Bandwidth Allocation, TDMA (Time division multiple access), Multiplexing, and 13 moreOptical physics, Dynamic Bandwidth Allocation, Cycle Time, Wavelength Division Multiplexing, Dynamic Channel Allocation, Simulation and Modeling, Time Division Multiplexing, Electrical And Electronic Engineering, Lightwave, Ethernet Passive Optical Network, Access Network, Single Channel, and Channel Allocation
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Research Interests: Optics, Medical Imaging, Fiber Optics, Telecommunications, Photonics, and 20 moreOrthogonal Frequency Division Multiplexing (OFDM), Next Generation Networks, Society, Quality of Service, Optical, Wimax, Light, Local Area Networks, Multiplexing, Network Capacity, Optical physics, Analytical Model, Perforation, Next Generation, Broadband Access, Admission Control, Wireless Communication, Electrical And Electronic Engineering, Optical Wireless, and Ethernet Passive Optical Network
ABSTRACT In this paper, we propose and experimentally demonstrate a reconfigurable long-reach (R-LR) UltraFlow access network to provide flexible dual-mode (IP and Flow) service with lower capital expenditure (CapEx) and higher energy... more
ABSTRACT In this paper, we propose and experimentally demonstrate a reconfigurable long-reach (R-LR) UltraFlow access network to provide flexible dual-mode (IP and Flow) service with lower capital expenditure (CapEx) and higher energy efficiency. UltraFlow is a research project involves the collaboration of Stanford, MIT, and UT-Dallas. The design of the R-LR UltraFlow access network enables seamless integration of the Flow service with IP passive optical networks deployed with different technologies. To fulfill the high-wavelength demand incurred by the extended service reach, we propose the use of multiple feeder fibers to form subnets within the UltraFlow access network. Two layers of custom switching devices are installed at the central office (CO) and remote node to provide flexibility in resource allocation and user grouping. With a centralized software-defined network (SDN) controller at the CO to control the dual-mode service, numerical analysis indicates that the reconfiguration architecture is able to reduce the CapEx during initial deployment by about 30%. A maximum of around 50% power savings is also achieved during low traffic period. The feasibility of the new architecture and the operation of the SDN controller are both successfully demonstrated on our experimental testbed.
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ABSTRACT In this paper, we propose and experimentally demonstrate a reconfigurable long-reach (R-LR) UltraFlow access network to provide flexible dual-mode (IP and Flow) service with lower capital expenditure (CapEx) and higher energy... more
ABSTRACT In this paper, we propose and experimentally demonstrate a reconfigurable long-reach (R-LR) UltraFlow access network to provide flexible dual-mode (IP and Flow) service with lower capital expenditure (CapEx) and higher energy efficiency. UltraFlow is a research project involves the collaboration of Stanford, MIT, and UT-Dallas. The design of the R-LR UltraFlow access network enables seamless integration of the Flow service with IP passive optical networks deployed with different technologies. To fulfill the high-wavelength demand incurred by the extended service reach, we propose the use of multiple feeder fibers to form subnets within the UltraFlow access network. Two layers of custom switching devices are installed at the central office (CO) and remote node to provide flexibility in resource allocation and user grouping. With a centralized software-defined network (SDN) controller at the CO to control the dual-mode service, numerical analysis indicates that the reconfiguration architecture is able to reduce the CapEx during initial deployment by about 30%. A maximum of around 50% power savings is also achieved during low traffic period. The feasibility of the new architecture and the operation of the SDN controller are both successfully demonstrated on our experimental testbed.
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ABSTRACT Passive optical network (PON) is regarded as a promising solution for the broadband bandwidth bottleneck problem. However, due to its passive nature, legacy PON is limited by the static power distribution, which makes it power... more
ABSTRACT Passive optical network (PON) is regarded as a promising solution for the broadband bandwidth bottleneck problem. However, due to its passive nature, legacy PON is limited by the static power distribution, which makes it power inefficient. To address this problem, we propose QPAR [4], a Quasi-Passive and Reconfigurable node, which enables dynamic power and wavelength assignment so as to save optical power budget in PON. In this paper, we study the power gains that can be achieved in PON employing QPAR, as well as different factors that may facilitate or prevent real QPAR deployments. We conduct extensive simulations to demonstrate the merits of QPAR. Results show that QPAR can achieve high optical power saving by intelligently redistributing the unnecessary power assigned to “close” optical network units (ONUs) in the network. The saved power can either be used to connect more ONUs, or extend the network reach without increasing the optical power budget.
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ABSTRACT Quasi-PAssive Reconfigurable (QPAR) devices can provide flexible power/wavelength distribution in next generation optical access networks. We experimentally demonstrate and analyze a high-dimension QPAR with one wavelength, four... more
ABSTRACT Quasi-PAssive Reconfigurable (QPAR) devices can provide flexible power/wavelength distribution in next generation optical access networks. We experimentally demonstrate and analyze a high-dimension QPAR with one wavelength, four power levels and four output ports.