Arshad Chowdhury

Bio: Arshad Chowdhury is an academic researcher from North South University. The author has contributed to research in topics: Radio over fiber & Wavelength-division multiplexing. The author has an hindex of 23, co-authored 126 publications receiving 2109 citations. Previous affiliations of Arshad Chowdhury include Wright State University & University of California.

Key Technologies of WDM-PON for Future Converged Optical Broadband Access Networks [Invited]

Abstract: The wavelength-division-multiplexed passive optical network (WDM-PON) is considered to be the next evolutionary solution for a simplified and future-proofed access system that can accommodate exponential traffic growth and bandwidth-hungry new applications. WDM-PON mitigates the complicated time-sharing and power budget issues in time-division-multiplexed PON (TDM-PON) by providing virtual point-to-point optical connectivity to multiple end users through a dedicated pair of wavelengths. There are a few hurdles to overcome before WDM-PON sees widespread deployment. Several key enabling technologies for converged WDM-PON systems are demonstrated, including the techniques for longer reach, higher data rate, and higher spectral efficiency. The cost-efficient architectures are designed for single-source systems and resilient protection for traffic restoration. We also develop the integrated schemes with radio-over-fiber (RoF)-based optical-wireless access systems to serve both fixed and mobile users in the converged optical platform.

Design and implementation of ultra-low latency optical label switching for packet-switched WDM networks

Abstract: An ultra-low latency, high throughput Internet protocol (IP) over wavelength division multiplexing (WDM) packet switching technology for next-generation Internet (NGI) applications has been designed and demonstrated. This method overcomes limitations of conventional optical packet switching, which require buffering of packets and synchronization of bits, and optical burst switching methods that require estimation of delays at each node and for each path. An optical label switching technique was developed to realize flexible bandwidth-on-demand packet transport on a reconfigurable WDM network. The aim was to design a network with simplified protocol stacks, scalability, and data transparency. This network will enable the NGI users to send their data applications at gigabit/second access speed with low and predictable latency (<1 /spl mu/sec per switch node), with a system capacity of beyond multi-Tb/s. Packet forwarding utilizes WDM optical headers that are carried in-band on the same wavelength and modulated out-of-band in the frequency domain.

Cost-Effective Optical Millimeter Technologies and Field Demonstrations for Very High Throughput Wireless-Over-Fiber Access Systems

Abstract: The broadband penetration and continuing growth of Internet traffic among residential and business customers are driving the migration of today's end user's network access from cable to optical fiber and superbroadband wireless systems The integration of optical and wireless systems operating at much higher carrier frequencies in the millimeter-wave (mm-wave) range is considered to be one of the most promising solutions for increasing the existing capacity and mobility, as well as decreasing the costs in next-generation optical access networks. In this paper, several key enabling technologies for very high throughput wireless-over-fiber networks are reviewed, including photonic mm-wave generation based on external modulation or nonlinear effects, spectrum-efficient multicarrier orthogonal frequency-division multiplexing and single-carrier multilevel signal modulation. We also demonstrated some applications in wireless-over-fiber trials using these enabling techniques. The results show that the integrated systems are practical solutions to offer very high throughput wireless to end users in optically enabled wireless access networks.

Advanced System Technologies and Field Demonstration for In-Building Optical-Wireless Network With Integrated Broadband Services

Abstract: This work describes a concept of a hierarchical radio-over-fiber (RoF) network architecture that provides both intra- and inter-network connectivity for end user wireline and wireless terminals with high-bandwidth, in-building access applications. An intelligent gateway router (IGR) is proposed as a unified platform to accommodate multi-gigabit, millimeter-wave services at 60-GHz band as well as being backward compatible with all current wireless access technologies such as WiFi and WiMAX. In addition, we further present an advanced multi-band optical carrier generation technique that can simultaneously deliver independent 60-GHz mm-wave, 2.4-GHz WiFi, and 5.8-GHz WiMAX signals efficiently carried over the same wavelength, and is suitable for the proposed IGR. Finally, we report, for the first time to our knowledge, a campus-wide field trial demonstration of RoF system transmitting uncompressed 270-Mbps standard definition (SD) and 1.485-Gbps high definition (HD) real-time video contents carried by 2.4-GHz radio and 60-GHz millimeter wave signals, respectively, between two on-campus research buildings distanced over 2.5-km standard single mode fiber (SMF-28) through the Georgia Institute of Technology's (GT) fiber network.

Simultaneous Generation of Independent Wired and Wireless Services Using a Single Modulator in Millimeter-Wave-Band Radio-Over-Fiber Systems

Abstract: We experimentally demonstrated a novel radio-over-fiber scheme to simultaneously obtain independent wired and wireless signals by using only a single intensity modulator. The optical 40- or 60-GHz millimeter-wave (mm-wave) carriers are generated by means of subcarrier-multiplexing techniques to carry 2.5-Gb/s wireless signals while 10-Gb/s wired signals are imposed on the original optical carrier via regular intensity modulation. The signals with dual services are successfully transmitted over 20-km single-mode fiber (SMF-28) with less than 1.5-dB power penalty.

Advanced Optical Modulation Formats

Abstract: Fiber-optic communication systems form the high-capacity transport infrastructure that enables global broadband data services and advanced Internet applications. The desire for higher per-fiber transport capacities and, at the same time, the drive for lower costs per end-to-end transmitted information bit has led to optically routed networks with high spectral efficiencies. Among other enabling technologies, advanced optical modulation formats have become key to the design of modern wavelength division multiplexed (WDM) fiber systems. In this paper, we review optical modulation formats in the broader context of optically routed WDM networks. We discuss the generation and detection of multigigabit/s intensity- and phase-modulated formats, and highlight their resilience to key impairments found in optical networking, such as optical amplifier noise, multipath interference, chromatic dispersion, polarization-mode dispersion, WDM crosstalk, concatenated optical filtering, and fiber nonlinearity

Guide to Biometrics

Abstract: This complete, technical guide details the principles, methods, technologies, and core ideas used in biometric authentication systems. It explains the definition and measurement of performance and examines the factors involved in choosing between different biometrics. It also delves into practical applications and covers a number of topics critical for successful system integration. These include recognition accuracy, total cost of ownership, acquisition and processing speed, intrinsic and system security, privacy and legal requirements, and user acceptance. The "Guide to Biometrics:" * Debunks myths and candidly confronts problems associated with biometrics research * Details relevant issues in choosing between biometrics, as well as defining and measuring performance * Defines and explains how to measure the performance of both verification and identification systems * Addresses challenges in managing tradeoffs between security and convenience Security and financial administrators, computer science professionals, and biometric systems developers will all benefit from an enhanced understanding of this important technology.

Labeled optical burst switching for IP-over-WDM integration

Abstract: The rapid pace of development in both Internet applications and emerging optical technologies is bringing about fundamental changes in networking philosophies. Key trends are the emergence of dynamic wavelength provisioning and a corresponding reduction in wavelength provisioning timescales. As this transition continues, the current use of the wavelength-routing paradigm for carrying bursty Internet traffic will likely suffer from various shortcomings associated with circuit-switched networks. Meanwhile, optical packet switching technology is still facing significant cost and technological hurdles. Optical burst switching, or OBS, which represents a balance between circuit and packet switching, has opened up some exciting new dimensions in optical networking. This article describes the OBS paradigm, and also proposes the use of labeled OBS, or LOBS, as a natural control and provisioning solution under the ubiquitous IP multiprotocol label switching framework.

Optical burst switching: a new area in optical networking research

Abstract: In this tutorial, we give an introduction to optical burst switching and compare it with other existing optical switching paradigms. Basic burst assembly algorithms and their effect on assembled burst traffic characteristics are described first. Then a brief review of the early work on burst transmission is provided, followed by a description of a prevailing protocol for OBS networks called just-enough-time (JET). Algorithms used as an OBS core node for burst scheduling as well as contention resolution strategies are presented next. Trade-offs between their performance and implementation complexities are discussed. Recent work on QoS support, IP/WDM multicast, TCP performance in OBS networks, and labeled OBS is also described, and several open issues are mentioned.

Fiber-Wireless Networks and Subsystem Technologies

Abstract: Hybrid fiber-wireless networks incorporating WDM technology for fixed wireless access operating in the sub-millimeter-wave and millimeter-wave (mm-wave) frequency regions are being actively pursued to provide untethered connectivity for ultrahigh bandwidth communications. The architecture of such radio networks requires a large number of antenna base-stations with high throughput to be deployed to maximize the geographical coverage with the main switching and routing functionalities located in a centralized location. The transportation of mm-wave wireless signals within the hybrid network is subject to several impairments including low opto-electronic conversion efficiency, fiber chromatic dispersion and also degradation due to nonlinearities along the link. One of the major technical challenges in implementing such networks lies in the mitigation of these various optical impairments that the wireless signals experience within the hybrid network. In this paper, we present an overview of different techniques to optically transport mm-wave wireless signals and to overcome impairments associated with the transport of the wireless signals. We also review the different designs of subsystems for integrating fiber-wireless technology onto existing optical infrastructure.