Nadiatulhuda Zulkifli

Recent development on time and wavelength-division multiplexed passive optical network (TWDM-PON) for next-generation passive optical network stage 2 (NG-PON2)

The second stage of next-generation passive optical network (NG-PON2) based on time and wavelength division multiplexed passive optical network (TWDM-PON) was proposed by a telecommunication group research to enhance the performance of broadband access networks. TWDM-PON was selected as the best candidate for NG-PON2 solution because of its ability to support the NG-PON2 requirements, such as enhanced bandwidth capacity, 40Gb/s, and coexistence with previously existing generations without any change to optical distribution network (ODN). This paper reviewed the recent progress carried out on a TWDM-PON system configuration, with emphasis on tunable transmitter and receiver optical network unit (ONU) in terms of the amount of tuning range reported in exploiting the wavelength plan provided with cost efficiency. The speed of data rate transmitted on the downstream and upstream links between optical line terminal (OLT) and ONU with the way of stacking approach in NG-PON2 is reviewed. In addition, the power system budget is reviewed to determine the number of users allocated with the system with each transmission allowed.

An overview of radio-over-fiber network technology

Current trends for future provision of broadband, interactive and multimedia services over wireless media in both mobile and fixed cellular networks are- 1) to reduce cell size to accommodate more users and 2) to operate in the microwave/millimeter wave (mm-wave) frequency bands to avoid spectral congestion in the lower frequency bands. The development of a cost-effective Base Station (BSs) is a key to be success in the market. Radio-over-fiber (RoF) technology is a promising solution for this requirement. This technique involves modulating the radio frequency (RF) subcarrier onto an optical carrier for distribution over a fiber network. Optical fibers are attractive for RoF systems due to the following characteristics: very high bandwidth, low loss, immune to EMI, light weight, small cross section, low cost, and high flexibility. Such an advantageous system will be presented throughout this paper including the backgrounds, architectures, benefits and limitations, and its milestone.

Moving Towards Upgradeable All-Optical Networks through Impairment-aware RWA Algorithms

We propose an impairment-aware RWA algorithm that allocates a lightpath for services with different interface requirements at 10 Gb/s and 40 Gb/s across a common transparent optical network. Significant benefits are demonstrated when compared with existing techniques.

Efficient resource allocation of heterogeneous services in transparent optical networks

Feature Issue on Transmission in Optically Transparent Core NetworksTransparent optical networking provides a common optical transport platform for services with different bit rates, transmission formats, and technologies that is adaptive to varying traffic demands from either edge aggregation networks or high-bandwidth end users. This paper describes a method of efficiently allocating resources to heterogeneous services that have diverse optical performance requirements at 10 and 40Gbit/s in terms of tolerance to chromatic dispersion (CD) and optical signal-to-noise ratio degradations. We particularly focus on exploiting the wavelength-dependent nature of CD and demonstrate that by including such information in the routing subproblem and introducing a new just-enough wavelength assignment method, significant improvements in resource utilization can be obtained.

The Characterization of Radio-over-Fiber Employed GPON Architecture for Wireless Distribution Network

already congested to high frequency of operations. However, the operations in smaller (micro-/pico-) cells lead to the increasing of hardware development costs while working in high frequency majorly suffers from high signal attenuation. Lined up with the popularity of wireless networks, optical technology has also played an important role in the telecommunication world. Fiber optic is widely used in the backbone network due to its high BW (up to THz) and low attenuation (~0.2 dB/km) characteristics. Thus, fiber optic is promising to be the core of wireless networks. The integration of wireless and fiber is known as Radio-over-Fiber (RoF) which complements the flexibility of wireless signal and the advantageous properties of fiber optics. Technically, RoF is a hybrid system that integrates the wireless and optical in one system leading towards high capacity, high data rate, transparent and mobility solution [2]. RoF allows the cost reduction and easier controlling and upgrading by a centralized architecture that connects a number of Remote Base Station (RBSs) to the Central Station (CS).

Improved dynamic bandwidth allocation algorithm for XGPON

Passive optical networks (PONs) require a dynamic bandwidth allocation (DBA) algorithm at the optical line terminal for efficient utilizationofupstreambandwidth among the optical network units (ONUs) as per the quality of service requirements for each traffic class defined by PON standardizing bodies. The GigaPON access network (GIANT) was the first International Telecommunication Union compliant DBAalgorithm, which is further improved by Immediate Allocation with Colorless Grant (IACG) and Efficient Bandwidth Utilization (EBU) algorithms. However, the polling mechanism of IACG and EBU may not report the true bandwidthdemandofONUsduring a service interval. Furthermore, ONU scheduling mechanisms give preference to best effort traffic over the assured traffic during recursive allocation cycles in a service interval, which results in an increase in upstream delays for the assured traffic class. This paper presents an improved bandwidth utilization (IBU) algorithm, which rectifies these deficiencies with a novel polling and scheduling mechanism. Experimental results show that IBU improves the mean of upstream delays of type 2 traffic up to 98%, 93%, and 76% and up to 99%, 92%, and 73% for type 3 traffic compared to the GIANT, IACG, and EBU algorithms, respectively. IBU also shows the least frame loss compared to these state-of-the-art algorithms.

Analysis of the next generation green optical access networks

This article provides a critical review on the feasibility of green next generation optical access network (NG-OAN), where a range of technologies are involved. It discusses some relevant representatives in the area where in specific access technologies based on Wavelength Division Multiplexing-Passive Optical Networks (WDM-PON) have been identified as the key promising green solutions. The impacts of other networking functionalities e.g. traffic aggregation and protection on the NG-OAN are also included in the review. With this, the issues, challenges and research vision are outlined that highlight the ongoing and future directions of green NG-OAN.

Comprehensive Polling and Scheduling Mechanism for Long Reach Gigabit Passive Optical Network

Abstract Dynamic bandwidth assignment (DBA) schemes for long reach PONs face a suffer from higher upstream channel idle time due to long round trip time (RTT). In ITU PONs, the DBA schemes; Immediate allocation with colorless grant (IACG), Efficient bandwidth utilization (EBU) and GPON redundancy eraser algorithm (GREAL) minimize idle time by sending bandwidth grants to the optical network units (ONUs) every downstream frame (DF). EBU further improves IACG by utilizing unused bandwidth (UBW) of other traffic classes. Sending the grant results every DF requires optical line terminal (OLT) to remember all previous grants sent to ONU during RTT and subtract them from the received queue reports. Since, both IACG and EBU assign the excess bandwidth equally to ONUs. Therefore, the OLT is actually not aware of the complete grant to each traffic class and thus do not subtract these completely from receiving reports. This leads to wastage of bandwidth and higher US delays due to over granting. GREAL resolves this problem by not utilizing the excess bandwidth which also leads to increased US delays. The proposed scheme in this study eliminates this shortcoming by allocating excess bandwidth to each traffic class completely at the OLT. Moreover, the UBW assignment mechanism of EBU is also improved. Simulation results show a 50–85 % reduction in delays of type-2 (T2) and type-3 (T3) traffic classes versus GREAL and IACG and up to 40 % reduction in delays for type-4 (T4) versus EBU.

Comparative analysis of cyclic and watchful sleep modes for GPON

Decreasing the power consumption of Passive Optical networks to reduce GHG emissions and CAPEX using ONT sleep mode is a widely researched topic. Different sleep mode mechanisms have been proposed in the literature. Cyclic sleep was adopted by ITU-T for XGPON in 2010 but recently a new sleep mode mechanism termed as Watchful sleep mode has been introduced for both GPON and XGPON. In this study, we have performed a comparative performance analysis of both of these sleep modes. Our results show that Watchful sleep mode consumes slightly more power but offers much lesser state transition delay compared to cyclic sleep mode.

Capacity improvement of TWDM-PONs exploiting the 16-QAM technique for downstream side with a nonlinearity effect study for upstream DML

Currently, the main goal of developing time-wavelength- division multiplexing passive optical networks (TWDM-PONs) is to acquire capacity improvement in a scalable and cost-effective manner. In response to the challenge, this paper demonstrates a full-system TWDM-PON through physical layer simulation that provides 56 Gb/s downstream and 40 Gb/s upstream bandwidths. We propose a simple and cost-effective scheme to improve the capacity of the downstream signal by utilizing highly spectrally efficient 16 quadrature amplitude modulation (QAM) with 20 GHz radio-over-fiber signal distribution using a single sideband signal that is generated by an optical dual-arm modulator. In addition, we study the effect of nonlinearity on a directly modulated laser (DML) as the upstream laser of an optical network unit. The outcomes obtained revealed good transmission quality in both directions, where bit error ratios of 10-6 and 10-5 are obtained for the downstream and upstream transmissions, respectively. This leads to the ability to support up to 128 users over 40 km of single-mode fiber.