IJRIT International Journal of Research in Information Technology, Volume 2, Issue 4, April 2014, Pg: 732- 739

International Journal of Research in Information Technology (IJRIT)

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ISSN 2001-5569

Review Paper on Multifarious Optical Networks Differentiated on the basis of various Multiple Access Techniques Roopali Gaur1, Ankur Singhal2, Kudip Pahwa3 1

2

Student, Department of ECE, M.M.U. Mullana Ambala, Haryana, India [email protected]

Associate Professor, Department of ECE, M.M.U. Mullana Ambala, Haryana, India [email protected] 3

Professor, Department of ECE, M.M.U. Mullana Ambala, Haryana, India [email protected]

Abstract The steady increase in the demand for broadband services and the consequent increase in the volume of generated traffic in our communication networks have motivated the need to implement next generation networks in our territories. Moreover, the fact of using passive optical network technology assumes the elimination of repeaters and optical amplifiers and therefore reducing the initial investment, lower power consumption, less space, fewer points of failure. A vast numbers of journals and research papers have been published regarding multifarious optical networks and multiple access techniques used in these networks. Outcome of some of the papers has been reviewed in this paper.

Keywords: Amplifiers, Passive optical networks, Repeaters.

1. Introduction A passive optical network is a network which by its nature provides a variety of broadband services to users through optical fiber access. PON allows removing all active components between the server and client introducing in place optical passive components to guide the traffic throughout the network. Its principal element is the optical splitter. The usage of passive architecture can reduce costs and are mainly used in FTTH networks. By contrast, the bandwidth is not dedicated, but rather multiplexed in a single fiber in the network access points. In short, this is a point-to-multipoint configuration network. Moving from the network to the user, it can say that PON architecture consists of the following equipment: an Optical Line Terminal (OLT) at the service provider’s central office and a number of Optical Network Units (ONUs) or Optical Network Terminals (ONTs) close to end users.

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2. Reviews Simple Uplink SOA – Pattern Effects Compensation for Reach Extended 10G-EPONs Claudio Porzi, Yasuyuki Kado, Satoshi Shimizu, Akihiro Maruta, Naoya Wada, Antonella Bogoni, and KenIchi Kitayama (Jan/2014) In this paper an uplink in-line semiconductor optical amplifiers (SOAs) for reach – extended, high speed passive optical networks is proposed and experimentally demonstrated enabling strong pattern effects mitigation. In this technique, a low power CW assist light (AL), at shorter wavelength that the data signal, is selectively injected into the saturated amplifier. This clamps the amplifier’s gain without affecting the useful gain at the data wavelength in the high input power regime. This is done when the power level of input data triggers pattern effects in the SOA at the 1.3µm data wavelength, in the presence of AL. For a transmitted data ER of 7dB, it is experimentally verified at 10Gb/s that ASL dynamic range increase as large as 7dB which is worst polarization case. The method proposed by the authors is transparent to the bit rate and avoids expensive high frequency opto-electronics circuitry making it suitable for future 10G and hybrid XG-PON. [1] Optimization of Survivable Mesh Long- Reach Hybrid WDM-TDM PONs Dieu Linh Truong, Phan Thuan Do, and Anh T. Pham (Jan/2014) Deploying access networks for remote service areas with thousands of customers can be done with long reach hybrid wavelength division multiplexing (WDM) and time division multiplexing (TDM) passive optical networks (PONs). In order to feed the service area with data flows, several long fiber cables run between the central office (CO) of the service provider and each service area. In the service area, array waveguide gratings (AWGs) are used to multiplex and demultiplex wavelength after that splitters are used to split wavelength in order to serve multiple optical network units. Mesh links are used between AWGs which helps in reducing the fiber installation and maintenance costs of long reach access networks avoiding unnecessarily long fibers between COs and service areas. The use of a mesh topology in service areas is proposed in this paper. There are two main advantages of this architecture. First, the network structure becomes more robust because of mesh linkages between AWGs with a high possibility of integrating survivable schemes. Second, leading to a reduction of total length of fiber deployment, fewer fibers are required between the CO and service areas, which reduces fiber installation and maintenance costs. Following this architecture authors developed efficient heuristic algorithms for designing the topology. In this all connections between OLTs and ONUs are survivable upon any single failure. According to the experiments done by authors, about 86% of optimal network topologies should use links between AWGs. Results of this paper show that the heuristic algorithms find solution very close to optimal ones. [2] Fiber Powered Extender for XG-PON/G-PON Applications Rivael S. Penze, João B. Rosolem, Ulysses R. Duarte, Getulio E. R. Paiva, and Renato Baldini Filho (Mar/2014) In this work a new approach to power passive optical network (PON) extenders is proposed which turns them virtually passive using power over fiber technique. A comparison between the conventional method to power the extenders and the presented POF technique is described. The approach presented by the authors improves the reliability and the security of the system by eliminating the batteries in the remote sites. Based on the extender the performance of fiber powered semiconductor optical amplifier is shown with a 10 gigabit passive optical network (XG-PON) /gigabit passive optical network (G-PON) system setup using a 1:32 splitter and 50Km reach. Authors believe that the maximum optical powering link distance can be increased as the technology of the PV continues to improve and novel low-consumption opto electronic devices such as RSOAs become available. [3] Multipoint Control Protocol with Look- Ahead for Wavelength Division Multiplexed Ethernet Passive Optical Network Xiaomin Liu, George N. Rouskas, Feng He, and Huagang Xiong (Feb/2014) In this research work authors presented a simple yet effective enhancement to the operation of the Ethernet passive optical network (EPON) multipoint control protocol (MPCP) for wavelength division multiplexing (WDM) EPON which allows for look ahead scheduling of the upstream channels. The look ahead operation can be implemented to the OLT via software updates without affecting the operation of optical network units in EPON as this operation is fully compatible with the existing standard. Significant performance gain Roopali Gaur,

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is achieved across a wide range of traffic loads by the look ahead enhanced MPCP operation. This also opens up new opportunities for the design of sophisticated dynamic bandwidth algorithms to support advanced quality of service capabilities. [4] Time- and Wavelength-Division Multiplexed Passive Optical Network (TWDM-PON) for NextGeneration PON Stage 2 (NG-PON2) Yuanqiu Luo, Xiaoping Zhou, Frank Effenberger, Xuejin Yan, Guikai Peng, Yinbo Qian, and Yiran Ma (Feb/2013) In this paper authors investigated the basics of TWDM-PON. Its critical features are reviewed to meet the NG-PON2 requirements. TWDM-PON uses research and development in PON industry to its maximum by stacking four XG-PON to reach an aggregate access rate of 40Gb/s. TWDM-PON research in FSAN is summarized by reviewing the basics and presenting the world’s first full system 40Gb/s TWDM-PON prototype. In the access network market, network upgrade requirement and the cost model consideration are balanced by TWDM-PON. After introducing the TWDM-PON architecture, its wavelength plan options are explored to meet the NG-PON2 requirements. For this purpose two applications are considered. First one is pay-as-you-grow provisioning. In this application, the operators can address the bandwidth growth demand by investing for what is needed and to expanding on demand. Second application of TWDM-PON is for local loop unbundling. The shared infrastructure for multiple operators is unbundled by this scheme. After that major wavelength plans are discussed and their loss budgets are evaluated. Wavelength plans like reusing the XG-PON wavelength bands and redefining the C-band enhancement band are discussed. Then some key enabling technologies of tunable ONUs, ONU Tunable Receiver and ONU Tunable Transmitter are summarized. This research shows that there are multiple candidate technologies and if any one technology does not perform to expectation then there are always other options to implement the required functions. In this research, a full system TWDM-PON prototype is demonstrated for the first time which integrates commercial components to provide 40Gb/s in downstream and 10Gb/s in upstream. In this prototype, in colorless ONUs tunable lasers and tunable filters are employed with the power budget of 40dB in downstream and 38dB in upstream. This supports a total split ratio of 1:512 and a distance of 20Km. And at last a joint lab test is demonstrated which shows the successful coexistence of G-PON, XGPON and TWDM-PON with any degradation in service. [5] Colorless Optical Transmitter for Upstream WDM PON Based on Wavelength Conversion Zaineb Al-Qazwini, Madhan Thollabandi, and Hoon Kim In this research paper, a novel colorless optical transmitter is proposed and demonstrated by the authors, which is based on all optical wavelength conversion for upstream WDM-PON system. The ONU side of the proposed optical transmitter is composed of an electro-absorption modulated laser, an optical coupler and a reflective semiconductor optical amplifier. Therefore, through monolithic integration, it could be implemented potentially in a cost effect manner. Through cross gain modulation, a gain saturated RSOA is used to imprint the upstream data generated by the EML onto the continuous wave seed light provided from the central office. To improve the bandwidth and the dispersion tolerance of the system, an optical delay interferometer at the central office tailors the chirp of the converted upstream signal. In this research paper experimental demonstration is performed at 10.7Gb/s which shows that the proposed scheme works over 30nm of either the pump or probe wavelength. As the EML wavelength can be chosen arbitrarily within this wavelength range therefore the proposed optical transmitter operates in a colorless manner and moreover based on directly modulated semiconductor opto-electronic devices. The modulation bandwidth is basically limited by the carrier lifetime in the active layer and hence the performance of the proposed transmitter is limited by fast carrier dynamics of the RSOA. Thus, in this research it is expected by the authors that the proposed scheme could be used as an alternative solution to reflective electro-absorption modulator SOA based transmitter to implement high capacity WDM PONs operating at 10Gb/s/channel and beyond. [6] Automatic Wavelength Allocation Method Using Rayleigh Backscattering for a WDM-PON With Tunable Lasers Sang-Rok Moon, Hoon-Keun Lee, and Chang-Hee Lee (Mar 2013) In this research paper authors proposed an automatic wavelength control method using Rayleigh backscattering in a feeder fiber for tunable lasers employed in a wavelength division multiplexing passive optical network. Two different realization methods are demonstrated in this research, maximizing Roopali Gaur,

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backscattered power and maximizing the second harmonic component with wavelength modulation. Their impact on the transmission performance and their limiting factors are also investigated and for this a VCSEL, a low cost tunable light source is used. As seen in this research the use of a broader AWG pass band degraded the wavelength match while the system penalty for the power monitoring case is reduced. In case of wavelength match while the system penalty for the power monitoring case is reduced. In case of wavelength modulation, to have the same conversion rate from the wavelength to intensity modulation should be increased. Though, the power penalty provided by a flat wavelength modulation efficiency of a tunable laser can be almost the same. The penalty induced by wavelength mismatch increases for a constant mismatch with the increased in data rate. If the sensitivity of the 2f detection is improved then these penalties can be reduced. It is noted from this research that if the tuning range of the tunable laser is wider than the free spectral range of the AWG then to restrict the tuning range, an optical band pass filter or control of the tuning signal is needed. In this work, an automatic wavelength allocation method for a WDM-PON with tunable lasers is proposed and analyzed by the authors. In the transmission fiber to identify and to lock the wavelength of the tunable laser to the desired wavelength, the intrinsic Rayleigh backscattering is used. Two approaches can be used to realize the proposed methods, firstly, by measuring the backscattering power and secondly by measuring the 2f spectrum with a wavelength modulation at frequency f. Authors investigated the characteristics and limits of both the methods. By the proposed method the power penalty induced is negligible. Regardless of the type of tunable lasers, both methods are useful for realizing a cost effective WDM-PON. The 2f detection method is preferable for a tunable laser that has a large output power change like the VCSEL used in this research work. [7] Dynamic Bandwidth Allocation With SLA Awareness for QoS in Ethernet Passive Optical Networks Abhishek Dixit, Bart Lannoo, Goutam Das, Didier Colle, Mario Pickavet, and Piet Demeester (Mar/2013) In Ethernet Passive Optical Networks, Quality of Service(QoS) is a crucial concern. In this research work authors proposed a new dynamic bandwidth allocation (DBA) algorithm that meets the service level agreements (SLAs) of the users for service differentiation. Authors proposed MDAWS algorithm for the high priority traffic classes and DAGS algorithm for medium priority traffic classes. On one side these proposed DA algorithms imparts a high jitter performance on the other side, helps in achieving a high throughput. For both, high priority traffic and medium priority traffic classes, these proposed algorithms achieve a centralized delay distribution. Moreover, the variance of the delay is load independent. A high throughput of 96% is achieved by the proposed DA algorithms. It provides constant and predictable average packet delay and reduced delay variation in case of high & medium priority traffic, with keeping the packet loss rate under check. Centralized QoS control is implemented by the algorithms which make it more interoperable and efficient. Concept of DP for SLA awareness is also proposed in this work. The delay requirement of the prioritized traffic classes is accomplished with the increase is throughput and the ONUs with different delay bound requirements is polled according to their needs. In this work authors also proved the effectiveness of the proposed concepts in LR-PON with upstream line rates of 10 and 40G with a larger reach (100Km) and a higher number of users (128), by exhaustive simulations. [8] Experimental Demonstration of a 10 Gb/s Subcarrier Multiplexed WDM PON Jonathan M. Buset, Ziad A. El-Sahn, and David V. Plant (Aug/2013) In this work a 10Gb/s bidirectional subcarrier multiplexed (SCM) wavelength division multiplexed (WDM) passive optical network (PON) is experimentally demonstrated by the authors. Demonstration of SCM WDM PON takes place with symmetric 10Gb/s bidirectional transmission over a single 20Km feeder. To optimize the performance of low cost IM/DD optoelectronic transceivers, DSP spectral pre-compensation and offset optical filtering techniques are used in this architecture. Using digital signal processing and square root raised cosine pulse shaping techniques; M-ary quadrature amplitude modulation electrical signals are generated for the downlink and uplink transmission. For this simple intensity modulation and direct detection optoelectronics and 10GHz transceivers are used. The design proposed by the authors includes spectral pre-emphasis and offset optical filtering. These designs increase the effective bandwidth of a commercial 2.2GHz reflective semiconductor optical amplifier based optical network unit. In the design of this research work symmetric 10Gb/s transmission over a 20Km single feeder PON with optical line terminal launch powers from 1 to 9dBm is realized. The authors also demonstrated the ability of SCM WDM PONs to withstand the effects of upstream impairments. For this a wide range of launch powers from 1dBm to 9dBm is considered for the operation. [9] Roopali Gaur,

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Standards-Compliant EPON Sleep Control for Energy Efficiency: Design and Analysis Jingjing Zhang, Mina Taheri Hosseinabadi, and Nirwan Ansari (July/2013) Reduction of energy consumption of optical access network has become an important problem for network designers. In this paper reduction of energy consumption of optical network units (ONUs) in an Ethernet Passive Optical Network (EPON) is mainly focused. In this work authors proposed a simple sleep control scheme that efficiently puts EPON ONUs into the sleep mode for energy saving. In EPON, downstream traffic is broadcasted to all ONUs by the optical line terminal (OLT), located at the central office. Each ONU checks all arriving downstream packets to obtain the packet destined to it. Therefore, it is necessary for the receivers at ONUs to stay aware and consume a large amount of energy. In this proposed scheme, two main parts are constituted in which downstream traffic scheduling rules at the OLT and sleep control rules at ONUs. There is no requirement of modification of EPON MAC protocol in this sleep control scheme, moreover, it eliminates the need for the handshake process and allows dynamic downstream bandwidth allocation, because of which high efficiency is achieved in both energy saving and bandwidth utilization. In this work, authors theoretically analyze the impacts of different parameters in the sleep control scheme on the delay and energy saving performance by using Semi-Markov chains. At last it is shown that the proposed scheme can save 50% of the ONU receiver energy with the proper settings of sleep control parameters. [10] Highly Flexible and Efficient Model for QoS Provisioning in WDM EPON Mirjana R. Radivojevic´ and Petar S. Matavulj (Aug/2013) Conventional single channel Ethernet Passive Optical Network (EPON) cannot fully realize the need of higher bandwidth and a faster access network for the recent development of new applications and services. The realization of WDM EPONs is the best solution in such circumstances where converged triple play networks are implemented. In this paper authors proposed a novel DWBA model for a hybrid TDM/ WDM EPON with full QoS support. Here a novel algorithm dynamic wavelength priority bandwidth allocation is presented with Quality of Service (QoS) support which also incorporates both offline and modified online scheduling, making the system more efficient and cost effective. Authors presented an approach to implement QoS support, where wavelength assignment takes place per service class and not per optical network unit. An additional subcycle is introduced which slightly degrades system performance in the control plane but the utilization of available upstream bandwidth in increased for transferring data in each wavelength channel. However, an efficient and equitable allocation of additional resources is provided by the existence of dynamic cycle with respect to the defined QoS policies. Using an original network model developed in MATLAB, extensive simulations have been gone through to test system characteristics. All the key parameters of a real network environment are incorporated in this such as queuing, transmission and packet processing delay, RTT and framing overhead among others. In the case of implementation of different traffic profiles, results are observed from the multiple simulations. From the obtained simulation results authors concluded and confirm the excellent performance of the presented model in all key QoS parameters, including average packet delay, jitter and packet loss rate and ensure superiority when it is compared with other DWBA models. Through this work authors believe that the DWPBA-TCH may serve as a respective candidate for wavelength and bandwidth allocation in NGN EPONs. [11] Self-Seeding of Semiconductor Lasers for Next-Generation WDM Passive Optical Networks M. Presi, A. Chiuchiarelli, R. Corsini, E. Ciaramella (2013) Among the sources of WDM-PONs self seeding of Reflective Semiconductor Optical Amplifiers (R-SOAs) and Fabry Perot lasors are the most promising ones. Self seeding is a mature technology for 1.25/2.5 Gb/s WDM-PON system with self tunability and very low cost. With commercially available components uncooled and polarization stable operations are easily feasible and can be implemented shortly in commercial units. Application of self seeding in real WDM-PONs is not trivial as it is intrinsically a polarization dependent process. In this paper authors reviewed novel approaches to solve the polarization issues when using R-SOAs are uncooled FP lasers. Across the whole C-band, 1.25Gb/s and 10Gb/s operations are experimentally demonstrated. In this paper it is shown that this technique is mature for applications in next-generation WDM-PONs. Although from 10Gb/s operation it is demonstrated that this technology is still not mature for such data rates. In order to consolidate operations beyond 2.5Gb/s, there are still many options and configurations to be explored. [12] Roopali Gaur,

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Design of Directly Modulated Long-Reach PONs Reaching 125 km for Provisioning of Hybrid Wired–Wireless Quintuple-Play Service Tiago M. F. Alves, Maria Morant, Adolfo V. T. Cartaxo, and Roberto Llorente (Aug/2013) In this work authors experimentally demonstrated design tools for the quintuple play service provisioning in a long reach passive optical network (LP-PON) using off the shelf directly modulated lasers (DMLs). A radio-over-fiber bundle of multiformat orthogonal frequency division multiplexing (OFDM) signals provides quintuple play service including broadband wired internet, phone/voice data, wireless high definition TV, wireless data and home security / control. Providing gigabit Ethernet connectivity, this bundle consist a full standard worldwide interoperability for microwaves access signal, long term evolution signal, two worldwide band channels and an ad hoc OFDM signal and all occupies a multi octave band. In this work authors demonstrated an adequate selection of the signal level applied to the DML, usage of a fixed optical dispersion compensator that can be shared by all ONUs and unbalanced power sharing between the different OFDM signals as suitable design tools. These design tools achieve EVM complaint provisioning of two UWB channels, LTE, a WiMax and an OFDM-GbE signal coexisting in a directly modulated LR-PON with maximum reach of 125Km. It is shown in this work that using the directly modulated LR-PON infrastructure with an EVM margin exceeding 1dB for all the signals and for all LRPON reaches, the bundle of OFDM signals can be delivered to the users’ premises. Results show that LRPONs employing DMLs are a powerful and cost effective alternative to LR-PONs using external modulation for the provision of the quintuple play service to the end users. [13] Cost-Effective Scalable and Robust Star-Cross-Bus PON Architecture Using a Centrally Controlled Hybrid Restoration Mechanism Hehong Fan, Jianqing Li, and Xiaohan Sun (July/2013) With the increasing traffic carried by fiber access networks have become critical for their applicability. In this paper authors presented low-redundancy passive optical network (PON) architecture by using a starcross-bus topology. A scale differentiated, centrally controlled hybrid failure localization and restoration procedure is used by the authors, which show distinguished capabilities to provide protections for the feeder and distribution fibers and also flexible m: n shared protection for the transceivers in the OLT. With the local fiber failures restored without disturbing other wavelengths, at least m single point failed ONU groups in the network can be restored completely by using the centrally controlled hybrid protection mechanism. Analysis done by the authors show that the survivability of this architecture is superior to existing ring & dual feeder fiber star networks, with the restoration time needed being only 2.1-8.2ms. If compared with the former survivable WDM PONs, the cost for devices in the network can be lower as, about ¼ to ½ of the transceiver can be saved and the need for Oss and filters is also the fewest with the exception that more couplers are required. With the addition of 2 or 3 couplers the cost for the ONUs can remain nearly unchanged. Therefore, in this network, higher redundancy efficiency is realized in this way. At last applicability of the PON architecture is further proved by scalability calculations. In this network hundreds of to a thousand ONUs can be accessed under a 30-40dB loss budget. [14] Intra-ONU Bandwidth Allocation Games in Integrated EPON/WiMAX Networks Hui-Tang Lin and Ying-You Lin (June 2013) For next generation broadband access network, integration of Ethernet passive optical network (EPON) and WiMax technologies is regarded as a promising solution. To satisfy quality of service (QoS) and fairness requirements of various traffic classes efficient bandwidth allocation schemes are essential while implementing such networks. Interactions between the self interested EPON and WiMax service providers (WSPs) are neglected by the existing proposals used for solving the bandwidth allocation program. A two stage game theoretic framework for the intra ONU bandwidth allocation process is proposed by the authors in the study and interactions between the EPON and WSPs are taken into account. To distribute the bandwidth granted from the OLT between the Ethernet and WiMax buffer regions of the ONU, the intra ONU bandwidth allocation problem is formulated as a bankruptcy problem in the first stage. A Stackelberg game (non-cooperative market) and a coalition game (cooperative market), these two games are proposed to solve this bankruptcy problem. Results obtained from the simulation show both schemes field fair and efficient sharing of upstream bandwidth under various network dynamics. In the second stage, to satisfy the QoS requirements specified for each class of traffic by the respective Ethernet and users and WiMax cell. Distribution of the bandwidth allocated to the Ethernet traffic and WiMax traffic at the ONU buffer takes Roopali Gaur,

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place in the second stage. Results obtained from the simulation confirm the Stackelberg NBS and coalition NBS schemes both ensure efficient and fair distribution of the bandwidth among the different traffic classes under different market models. From the results it can be seen that the proposed schemes provide better QoS support than the VOB DBA scheme. [15]

4. Conclusions The growing popularity of mobile data services necessitates a rapid rise in network capacity not only on the air interface to the end user, but also in the backhaul network. The latter is quite important for the mobile operator business model, affecting capital investment, operational expenses, service deployment, and customer experience. Fiber infrastructure is inevitably the only long-term solution, and the deployment of passive optical networks presents an opportunity for a cost-effective, scalable, and future-proof solution. [16] In this review paper, some of the papers related to optical networks are reviewed. Authors demonstrated a number to things which are discussed here.

References [1] Claudio Porzi, Yasuyuki Kado, Satoshi Shimizu, Akihiro Maruta, Naoya Wada, Antonella Bogoni, and Ken-Ichi Kitayama, “Simple Uplink SOA – Pattern Effects Compensation for Reach Extended 10GEPONs,” IEEE Photonics Technology Letters, vol. 26, no. 2, Jan 15, 2014. [2] Dieu Linh Truong, Phan Thuan Do, and Anh T. Pham, “Optimization of Survivable Mesh Long- Reach Hybrid WDM-TDM PONs,” Journal of Optical Communication Network, vol. 6, no. 1, Jan 2014. [3] Rivael S. Penze, Joao B. Rosolem, Ulysses R. Duarte, Getulio E. R. Paiva, and Renato Baldini Filho, “Fiber Powered Extender for XG-PON/G-PON Applications,” Journal of Optical Communication Network, vol. 6, no. 3, Mar 2014. [4] Xiaomin Liu, George N. Rouskas, Feng He, and Huagang Xiong, “Multipoint Control Protocol with Look- Ahead for Wavelength Division Multiplexed Ethernet Passive Optical Network,” Journal of Optical Communication Network, vol. 6, no. 2, Feb 2014. [5] Yuanqiu Luo, Xiaoping Zhou, Frank Effenberger, Xuejin Yan, Guikai Peng, Yinbo Qian, and Yiran Ma, “Time- and Wavelength-Division Multiplexed Passive Optical Network (TWDM-PON) for NextGeneration PON Stage 2 (NG-PON2),” Journal of Lightwave Technology, vol. 31, no. 4, Feb 15, 2013. [6] Zaineb Al-Qazwini, Madhan Thollabandi, and Hoon Kim, “Colorless Optical Transmitter for Upstream WDM PON Based on Wavelength Conversion,” Journal of Lightwave Technology, vol. 31, no. 6, Mar 15, 2013. [7] Sang-Rok Moon, Hoon-Keun Lee, and Chang-Hee Lee, “Automatic Wavelength Allocation Method Using Rayleigh Backscattering for a WDM-PON With Tunable Lasers,” Journal of Optical Communication Network, vol. 5, no. 3, Mar 2014. [8] Abhishek Dixit, Bart Lannoo, Goutam Das, Didier Colle, Mario Pickavet, and Piet Demeester, “Dynamic Bandwidth Allocation With SLA Awareness for QoS in Ethernet Passive Optical Networks,” Journal of Optical Communication Network, vol. 5, no. 3, Mar 2013. [9] Jonathan M. Buset, Ziad A. El-Sahn, and David V. Plant, “Experimental Demonstration of a 10 Gb/s Subcarrier Multiplexed WDM PON,” IEEE Photonics Technology Letters, vol. 25, no. 15, Aug 1, 2013. [10] Jingjing Zhang, Mina Taheri Hosseinabadi, and Nirwan Ansari, “Standards-Compliant EPON Sleep Control for Energy Efficiency: Design and Analysis,” Journal of Optical Communication Network, vol. 5, no. 7, July 2013. [11] Mirjana R. Radivojevic´ and Petar S. Matavulj, “Highly Flexible and Efficient Model for QoS Provisioning in WDM EPON,” Journal of Optical Communication Network, vol. 5, no. 3, Mar 2013. [12] M. Presi, A. Chiuchiarelli, R. Corsini, E. Ciaramella, “Self-Seeding of Semiconductor Lasers for NextGeneration WDM Passive Optical Networks,” ICTON 2013. [13] Tiago M. F. Alves, Maria Morant, Adolfo V. T. Cartaxo, and Roberto Llorente, “Design of Directly Modulated Long-Reach PONs Reaching 125 km for Provisioning of Hybrid Wired–Wireless QuintuplePlay Service,” Journal of Optical Communication Network, vol. 5, no. 8, Aug 2013.

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[14] Hehong Fan, Jianqing Li, and Xiaohan Sun, “Cost-Effective Scalable and Robust Star-Cross-Bus PON Architecture Using a Centrally Controlled Hybrid Restoration Mechanism,” Journal of Optical Communication Network, vol. 5, no. 7, July 2013. [15] Hui-Tang Lin and Ying-You Lin, “Intra-ONU Bandwidth Allocation Games in Integrated EPON/WiMAX Networks,” Journal of Optical Communication Network, vol. 5, no. 6, June 2013. [16] T. Orphanoudakis, E. Kosmatos, J. Angelopoulos, and A. Stavdas, “Exploiting PONs for Mobile Backhaul,” IEEE Communications Magazine, Feb 2013.

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