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The paper demonstrates a spectrum slicing technique applied to PAM-4 modulated signal spectrum at 40 Gbaud baudrate for optical access networks. The spectrum slicing is shown in VPIphotonics simulation environment, where characteristics of key components are measured in the laboratory and loaded into the corresponding elements of the simulation setup. The spectrum of electrical baseband signal is sliced in four slices introducing an additional degree of freedom – higher data rate signals can be transmitted by re-using already-existing lower bandwidth transceiver components in an optical access network. This tackles the electronic bottleneck enabling the on-demand variable bandwidth allocation and extends the life span of opto-electrical components during network upgrades. Furthermore, the use of the proposed spectrum slicing technique has a positive side-effect when it comes to security concerns, as the signal spectrum is divided into slices. All slices are necessary to obtain the reconstructed signal and even if an eavesdropper gets most of the slices it is still not enough. The simulation results show that the proposed spectrum slicing and stitching approach is a viable solution to overcome the problem of limited frequency bandwidth of electrical components. [ABSTRACT FROM AUTHOR]

This paper presents the design of a convergent optical transport architecture for wireless and photonic sensor networks based on the optical access network deployed in Bogotá city. The proposed architecture is evaluated through the transport of services in subcarrier division multiplexing to enable the seamless transport of different standards such as WiFi, Bluetooth, Zigbee, SigFox, among others. The proposed design demonstrates high scalability given the distribution of the previously deployed network, enabling the incorporation of both optical sensors based on FBG and wireless sensors in locations with greater historical, economic, cultural and social relevance. The proposal presents an optimal response in terms of bit error rate (BER) and signal power in the multi-coverage zone for various interference parameters such as SS-RSRP, SS-RSRQ, and Throughput.

Due to significant developments in high transmission rate applications for big data analytics, cloud computing, and other next-generation 5G smart applications, today's access networks are under a lot of pressure to meet the high bandwidth needs. In this work, a bidirectional high capacity of 160 Gbps utilizing hybrid time and wavelength division multiplexing passive optical network (TWDM-PON) is simulated and investigated via OptiSystem software. The fiber Bragg grating (FBG) in the receiver sector for both the optical line terminal (OLT) and optical network unit (ONU) is employed to reduce the effect of linear chromatic dispersion until given permission to enhance the distance communication system for a symmetric 160 Gbps E2-class (TWDM-PON). According to the results, the maximum achieved link distance with an outstanding bit error rate of 10 − 9 is around 40 km and 70 km for the system without and with dispersion compensation, respectively. This represents an enhancement of about 75% which can support the next-generation passive optical networks stage 2 (NG-PON2) with a splitting ratio of 1:256. [ABSTRACT FROM AUTHOR]

During multi-dimensional optical transmission, because of photodetector (PD) operation as a square law detector, signals get distorted when they are modulated on polarization and phase due to interdimensional interference (IDI) by intensity-modulated signals. We propose an IDI mitigation technique using recurrent neural network for multi-dimensional optical transmission. The signal transmission performance of the proposed equalization technique was experimentally analyzed. The performance of the proposed system was verified using the symbol error rate (SER).

Due to the Internet's and communication systems' rapid technological and service development, communication networks have been impacted by a rise in intricacy. Optical networks, which are vital components of both the core and access networks in communication networks, face major obstacles due to the complexity of the system and the requirement for manual effort. To overcome the current limitations and address the issues with future optical networks, it is essential to install greater intelligence capabilities to enable autonomous as well as flexible network operation. The present study delivers a novel approach for transmission analysis-routing-improved multiagent communication using optical access networks. An optical access network is used here, and routing is handled dynamically using multi-agent communication. A federated convolutional component neural network is then used to analyse the data flow. Throughput, latency from end to end, lifetime of the network, route loss, and energy consumption are all measured experimentally and analysed. When designing the routing protocol, we first model the network as a decentralised multi-agent system and factor in factors like residual energy and connection quality. As a result, the network is better able to adjust to changes and the lifespan of the network may be prolonged. The proposed solution increased network throughput by 97%, decreased end-to-end latency by 54%, prolonged the life of the network by 6%, reduced route loss by 59%, and reduced energy consumption by 55%. [ABSTRACT FROM AUTHOR]

In Japan, against the backdrop of the spread of high-definition video-streaming services and network applications such as cloud storage and work applications, the provision of high-speed communication services is gaining pace, and the research and development of optical access networks to support these services is under high expectations. Jun-ichi Kani, a senior distinguished I researcher at NTT Access Network Service Systems Laboratories is playing a leading role in researching and developing new optical access networks for the beyond fifth-generation mobile communication system (5G)/6G era. We interviewed him about the progress of his research activities and his approach to research. [ABSTRACT FROM AUTHOR]

Optical access networks are the networks connecting users to telecom central offices, and current trends of increasing traffic, services for mobile devices, and low-latency or high-reliability edge computing are creating a range of new requirements that these networks must be able to accommodate. We have asked Distinguished Researcher Takahiro Suzuki to talk with us about software-based optical access network virtualization technology that will be able to handle such requirements. [ABSTRACT FROM AUTHOR]

A novel architecture with full-duplex direct communications (FDDC) between any two ONUs for optical access network is proposed in this paper. By designing combination switch ingeniously, the architecture is finished to realize FDDC between any two ONUs in wavelength division multiplexing passive optical networks. By utilizing interconnected optical fibers between ONUs, the network has achieved three-level protections (feeder optical fiber protection, distributed optical fiber protection and interconnected optical fiber protection). By constructing expansion module, the network can be flexibly expanded and optimized, and the CapEx and OpEx of network can be greatly reduced. Finally, by the simulation and analysis, the effectiveness of the proposed architecture is demonstrated. [ABSTRACT FROM AUTHOR]

With the aim of tackling insufficient security in the chaotic encryption algorithm for digital images in the Optical Access Network, a color image encryption scheme combining non-degenerate discrete hyperchaotic system and deoxyribonucleic acid (DNA) dynamic encoding is proposed. First, a new non-degenerate hyperchaotic system is constructed with all positive Lyapunov and more complex dynamic characteristics. Furthermore, the key sequence based on non-degenerate hyperchaotic system is generated using plaintext correlation to achieve the effect of a dynamic secret key. Next, a binary bit-planes permutation is performed on the image using one of the key sequences. Then, the chaotic key sequence is used to sequentially perform DNA encoding, obfuscation, and decoding. Finally, a binary bit-planes obfuscation is performed to obtain the final ciphertext. The research results show that the non-degenerate chaotic sequence can pass the NIST 800-22 test, and the corresponding encryption algorithm can resist various common attacks and has a strong anti-interference ability. In addition, the algorithm is verified on ARM-Embedded, which proves that the encryption system proposed in this paper is a feasible secure communication technology scheme. Therefore, the scheme proposed in this paper is helpful to provide new ideas for the design and application of high-security cryptosystem in optical access network. [ABSTRACT FROM AUTHOR]

This paper proposes a novel chaotic power division multiplexing (CPDM) for secure optical multiple access. The proposed CPDM can not only improve spectral efficiency and the user number by multiplexing spectrally overlaid OFDM signals at different power ratio, but also ensure the information security of the users by implementing chaotic encryption on the physical layer. The key space of the encryption scheme is up to ${10^{98}}$ , which can effectively resist the illegal acceptance. Furthermore, to meet future data traffic and multiple access demands, we first explore the beneficial combination of power dimension and mode dimension. A 30 Gb/s secure chaotic power division multiplexing and mode division multiplexing passive optical network (CPDM-MDM-PON) transmission over 5 km weakly coupled few-mode fiber (FMF) is experimental demonstrated. Experimental results show that, the proposed PON system has the appealing potential to attain high spectral efficiency and large traffic capacity and serve more users. The nonlinearity transmission impairments of single mode fiber and FMF are also investigated in this paper. [ABSTRACT FROM AUTHOR]

The scattered Optical Network Units (ONUs) in an optical access network have different propagation delays. In an Ethernet passive optical network (EPON) adopting the traditional Interleaved Polling with Adaptive Cycle Time (IPACT) scheme, such ONU propagation delay difference will waste network resources and will degrade both network delay performance and network energy efficiency in delivering low-latency services. In this article, to deal with the heterogeneous ONU propagation delays problem, two solutions are proposed and investigated. The first solution, namely the Upstream Postponing with ONU Dozing (UP-OD) scheme, is to properly postpone the upstream transmissions of those ONUs having relatively short propagation delays to improve channel utilization efficiency, and ONU doze mode is incorporated to enhance network energy efficiency. The second solution, namely the Identical Fiber Length with ONU Sleeping (IFL-OS) scheme, is to adopt an identical distribution fiber length for ONUs to enhance channel utilization, and ONU sleep mode is incorporated for energy consumption reduction. Simulation results show that both the UP-OD scheme and the IFL-OS scheme reduce network delay and improve network energy efficiency in delivering low-latency (

With the aim of tackling insufficient security in the chaotic encryption algorithm for digital images in the Optical Access Network, a color image encryption scheme combining non-degenerate discrete hyperchaotic system and deoxyribonucleic acid (DNA) dynamic encoding is proposed. First, a new non-degenerate hyperchaotic system is constructed with all positive Lyapunov and more complex dynamic characteristics. Furthermore, the key sequence based on non-degenerate hyperchaotic system is generated using plaintext correlation to achieve the effect of a dynamic secret key. Next, a binary bit-planes permutation is performed on the image using one of the key sequences. Then, the chaotic key sequence is used to sequentially perform DNA encoding, obfuscation, and decoding. Finally, a binary bit-planes obfuscation is performed to obtain the final ciphertext. The research results show that the non-degenerate chaotic sequence can pass the NIST 800-22 test, and the corresponding encryption algorithm can resist various common attacks and has a strong anti-interference ability. In addition, the algorithm is verified on ARM-Embedded, which proves that the encryption system proposed in this paper is a feasible secure communication technology scheme. Therefore, the scheme proposed in this paper is helpful to provide new ideas for the design and application of high-security cryptosystem in optical access network.

For the rapid increase in the number of optical line terminals (OLTs) and optical network units (ONUs) connected to the control center in the software defined optical access network (SDOAN) environment, the security problems caused by the communication between devices and the high cost caused by the introduction of security schemes, we propose a lightweight identity two-way authentication scheme (LTWA) based on the cryptographically generated address (CGA) algorithm combined with the hash generated address (HGA) algorithm. The scheme introduces the CGA algorithm and the HGA algorithm without third party participation, so as to complete the first authentication binding and the non-first authentication binding between the communication nodes respectively, which effectively prevents an attacker from forging or tampering with authentication interaction messages, thereby establishing an end-to-end trusted connection in the access network. We experimentally verify the proposed LTWA scheme. The simulation results show that the scheme guarantees the security interaction between communication nodes, and reduces the average computational overhead and the blocking rate caused by malicious attacks.

So far,existing works related to quality evaluation of channel mainly focused on equipment layer and network layer in optical access network.Most of researches lack synthesis evaluation methods covering physical layer,network layer and business layer.As a result,it is hard for administrators to judge the actual quality of channel by network monitoring completely and accurately.To solve this problem,key influence factors of channel quality in optical access network was analyzed firstly,and a comprehensive multi-layer-multi-index evaluation model of channel quality was proposed.Then a SA-BP neural network algorithm was designed to train the parameters of the proposed evaluation model to make the result more accurate.The simulation results show that the proposed method has higher accuracy and stability,and can improve the quality and efficiency of network operation and maintenance.

This work proposes a resilient wheel-based wavelength-division-multiplexed passive optical network optical access network architecture for backhauling network traffic. This proposed resilient architecture can efficiently support not only the fixed users but also the mobile users in the downstream direction under normal and failure operating scenarios, while minimizing the average traffic delivery time and without using extra redundant fibers for protection purposes. [ABSTRACT FROM AUTHOR]

We introduce a coherent receiver that, without DSP and/or polarization coding at the transmitter, requires no Polarization Beam Splitter and still is polarization-independent. It is experimentally demonstrated at 10 Gbit/s with a sensitivity of −37.6 dBm at FEC level. It can also be operated at higher bit-rates and finds application in high-speed access and datacenter networks. [ABSTRACT FROM AUTHOR]

We demonstrate 100 Gb/s/ $\lambda $ duo-binary PAM-4 (DB-PAM-4) transmission over 50 km standard single-mode fiber (SMF) in the O-band using a 20G silicon-based transmitter and a 25G optically-amplified PIN+TIA-based receiver for 100G PON downstream applications. Receiver sensitivities of −15, −14.5 and −12 dBm are achieved at a bit error rate (BER) below the low-density parity-check forward error correction (LDPC-FEC) threshold (i.e., $1\times 10^{-2}$) in back-to-back (B2B), and after 20 and 50 km, respectively using a 131-tap linear feed-forward equalizer (FFE) at the receiver. According to the results, a power budget of 20 dB can be achieved for 20 km transmission. Furthermore, we report the performance of 99 Gb/s (33 Gbaud) PAM-8 transmission and show that DB-PAM-4 provides 5.3 dB better sensitivity compared to PAM-8 at the LDPC-FEC threshold. [ABSTRACT FROM AUTHOR]

We propose a business/cost model for long-period changes of customer demands in FTTx networks. We show how to exploit this model in the formulation of a MIP optimization problem that, for a given sequence of customer demand vectors provides (when solved to the optimality) the absolute benchmark. The model is relatively complicated and cannot be directly applied to the optimization of real-world networks without a number of algorithmic tricks that are discussed in this paper. The presented approach has been implemented and tested against an example network instance. Test results are given and discussed in the paper. [ABSTRACT FROM AUTHOR]

We demonstrate 25 and 50 Gb/s four-level pulse amplitude modulation (PAM-4) transmission over 43- and 21-km standard single-mode fiber (SMF), respectively, using a silicon photonic 120° hybrid-based integrated simplified coherent receiver in the $C$ -band. The integrated receiver is composed of an edge coupler, a vertical grating coupler, a polarization splitter–rotator, a $3\times 3$ multimode interference coupler-based 120° hybrid, and three germanium p-i-n photodetectors. For 25 Gb/s PAM-4 transmission, we achieved the receiver sensitivities of −18, −17.5, −16.6, −14.5, and −9.8 dBm in back-to-back (B2B) and after 10.5, 21, 31, and 43 km, respectively, at a bit error rate (BER) below the hard-decision forward error correction (HD-FEC) threshold (i.e., $3.8\times 10^{-3}$) without using any receiver equalizer, while for the 50 Gb/s PAM-4 transmission, the receiver sensitivities of −13.6 dBm in B2B, and −13.5 and −11.6 dBm after 10.5 and 21 km are obtained using a 31-tap linear feed-forward equalizer (FFE), respectively. Furthermore, we achieved up to 44 Gb/s receiver equalizer-free PAM-4 transmission over 10.5 km below the HD-FEC. The characterization of the receiver at different wavelengths within the $C$ -band is provided as well. [ABSTRACT FROM AUTHOR]

An energy-efficient and survivable optical access network structure is proposed and investigated. Based on a structure model of multilayer-ring, the access network is divided into four layers and modules on a same layer are interconnected as a ring. Therefore, multiple paths are available for optical network units to access an optical line terminal, which not only provides convenience in traffic aggregation, but also guarantees the survivability of network. With this structure, quantities of standby modules are reduced to decrease both capital cost and power cost. Large part of power can also be saved by turning off idle modules through traffic aggregation. Moreover, by controlling the optical switches deployed in remote node, elastic reach access is realized as well since amplification is optional on transmission links. Theoretical and numerical analyses indicate that the scheme shows great advantages on power saving, network survivability, as well as the system flexibility, and its energy efficiency performance can be further improved by operating in conjunction with energy-efficient resource scheduling scheme. It provides a potential structure for next generation optical access network.

Based on the coherent optical reception technology,a cost-effective structure for the optical network unit (ONU) transceivers in ultra-dense wavelength division multiplexing passive optical network using a single directly modulated laser (DML)was proposed.To reduce the number of required light sources,only one DML was used in both upstream and downstream links.By experimental investigations,the impacts of driving amplitude and bias current on DML's performance were analyzed.Meanwhile,the impact of frequency spacing between upstream and downstream signal and the Rayleigh backscattering interference on system performance were investigated.The method has better performance of system receiving and can effectively reduce the cost and complexity of coherent passive optical network system.

The rapid growth of new services and emerging network scenarios has serious impact on the existing network infrastructure，and it is an inevitable trend to build a new，high-speed and efficient access network architecture.The challenges faced by the existing network were analyzed，and it was pointed out that high-speed broadband access，efficient resource utilization，support for heterogeneous resource control would be future trends in the evolution of optical access networks.Then the access network development was recalled，the overall architecture of software-defined optical access network was described，SDN idea and OLT pooling technology were introduced into optical access network，and the major key technologies were analyzed，including the flexible programmable optical layer techniques，fine flow table forwarding，control layer virtualization，and etc.Several typical application scenarios suitable for software-defined optical access network were also presented.All of these indicate that the research and development on software-defined optical access network will meet current challenges and ultimately be helpful to achieve the end-to-end flexible control in the entire network.

It is a key technical problem to locate failure correctly and perform protection switching for strong survivability in time and wavelength division multiplexing（TWDM）optical access network with dynamic wavelength scheduling. To solve the above problem, a cost-effective survivability protection scheme using control channel for fault location and based on dynamic wavelength scheduling was presented. For the scheme, the quantitative comprehensive analysis of survivability and cost was carried on. Analysis and calculations show that at the best the proposed scheme can pay only 1% of the cost for survivability protection and bring in 54% improvement in survivability. The proposed scheme can finish protection switching within 50 ms.

Hybrid WDM/TDM optical access network has evolved as a cost-effective solution to the higher requirements of bandwidth in the access network. Bandwidth allocation and scheduling mechanism have become critical issues in the optical access networks. In this paper, a novel upstream bandwidth optimization hybrid scheduling algorithm has been proposed in which optical network units can employ tunable wavelength for upstream transmission with a single optical source. Resources allocations have been done utilizing multi point control protocol and for wavelength scheduling the shortest length of channels have been computed. Investigation of the proposed algorithm for providing improved channel utilization has been performed and a comparative analysis has been done for validation. [ABSTRACT FROM AUTHOR]

We review recent advances in the field of fiber-wireless convergence to better support cloud radio access networks via high-speed low-latency mobile fronthaul between remote radio units and baseband units. We also present how digital signal processing (DSP) may be used to support both common public radio interfaces (CPRI) in a point-to-point architecture and Ethernet-based CPRI in a point-to-multipoint architecture to achieve high bandwidth efficiency and low processing latency. The use of DSP-enabled next-generation passive optical networks (PON), such as 50 Gb/s PON, to support mobile fronthaul in a resource-efficient manner will also be discussed. [ABSTRACT FROM AUTHOR]

Next-generation passive optical network stage 2 (NG-PON2) supports the wavelength routed optical distributed network (WR-ODN), power splitter optical distributed network or wavelength-selected optical distributed network (WS-ODN) and hybrid of both the architecture configuration. NG-PON2 is world’s first multi-wavelength passive optical network (PON) standard. The fiber dispersion and nonlinearity degrades the performance of NG-PON2 severely. Fiber nonlinearity depends on the optical launch power and fiber reach. This paper focuses on maximizing the network performance and maximizing the number of simultaneous users with error-free performance by optimizing the optical launch power respectively at dynamic reach and differential reach. The optical launch power is optimized to abate the fiber nonlinearity and significantly enhances the performance of NG-PON2 at dynamic fiber reach for Alcatel 6912 Teralight Ultra 1625 commercial fiber specification. Furthermore, precise values of the optimum launch power for the dynamic fiber reach, for different NG-PON2 architecture, under industrial fiber specification is meticulously obtained. It is identified that irrespective of both, WR-ODN and WS-ODN architecture configuration, optimum launch power remains constant. Power budget is calculated for both, maximizing the performance and maximizing the simultaneous number of users at differential reach and dynamic reach of the NG-PON2. [ABSTRACT FROM AUTHOR]

We demonstrate 25-Gbit/s four-level pulse amplitude modulation transmission over 28-km standard single-mode fiber using an off-the-shelf 10-Gbit/s electro-absorption modulated laser and a $3\times3$ fiber splitter based simplified coherent receiver in the $C$ -band. No digital signal processing and dispersion compensation have been used either at the transmitter or at the receiver. Furthermore, the use of an intensity modulated signal allows us to avoid the phase and frequency locking of the local oscillator. We achieved receiver sensitivities of −18.25, −17, and −13.4 dBm at a bit error rate below the hard-decision forward error correction threshold (i.e., $3.8\times 10^{-3}$) and power budgets of 20.80, 19.55, and 15.95 dB in back-to-back, after 20.7 and 28 km, respectively. We also demonstrate polarization independent operation by slightly modifying the architecture of the simplified coherent receiver. [ABSTRACT FROM AUTHOR]

Nonlinear distortion from a directly modulated laser (DML) is one of the major limiting factors to enhance the transmission capacity beyond 10 Gb/s for an intensity modulation direct-detection optical access network. In this letter, we propose and demonstrate a low-complexity nonlinear equalizer (NLE) based on a machine-learning algorithm called artificial neural network (ANN). Experimental results for a DML-based 20-Gb/s signal transmission over an 18-km SMF-28e fiber at 1310-nm employing pulse amplitude modulation (PAM)-4 confirm that the proposed ANN-NLE equalizer can increase the channel capacity and significantly reduce the impact of nonlinear penalties. [ABSTRACT FROM AUTHOR]

Introduction of spatial division multiplexing (SDM) has added a new dimension in an effort to increase optical fiber channel capacity. At the same time, it can also be explored as an advanced optical networking tool. In this paper, we have investigated the resource allocation to end-users in multidimensional networking structure with plurality of spectral and spatial modes actively deployed in different networking segments. This presents a more comprehensive method as compared to the common practice where the segments of optical network are analyzed independently since the interaction between network hierarchies is included into consideration. We explored the possible transparency from the metro/core network to the optical access network, analyzed the potential bottlenecks from the network architecture perspective, and identified an optimized network structure. In our considerations, the viability of optical grooming through the entire hierarchical all-optical network is investigated by evaluating the effective utilization and spectral efficiency of the network architecture. [ABSTRACT FROM AUTHOR]

This paper shows the concept of the elastic lambda aggregation network (EλAN) that will achieve an elastic common access infrastructure for the metro-access network. It proposes a service restoration technique that uses optical path switching and intercentral office handover for EλAN to recover from disasters. The feasibility of the proposed service restoration technique is successfully demonstrated for the first time by using a prototype testbed of a metro-access network. By applying both orthogonal frequency division multiplexing and adaptive modulation, the system automatically changes the transmission parameters (modulation level, the number of subcarriers, and symbol rate) according to the service requirements and conditions of the optical distribution network, such as the link's end-to-end optical loss, in order to achieve accommodate multiple services. In the experiment, an optical network unit in a faulted system automatically reconnected within 10 s to another office 20-km away with the same throughput. [ABSTRACT FROM AUTHOR]

This paper proposes a resilient, bandwidth scalable and energy efficient WDM-TDM passive optical network (PON) architecture that provides network access services to the end user at very high data rates and reduces the power consumption of access network significantly in the presence of low traffic/underutilized network. The proposed power saving technique includes the efficient use of proper line cards (LC) and adaptive link rate (ALR) mechanism at optical line terminal located at the central office. In the presence of low traffic, ALR switches link rate from 10 to 1 Gbps depending on the particular threshold value of traffic load. In the presence of narrowband traffic, a significant amount of energy is saved. Proposed architecture also saves capital expenditure (CAPEX) at remote node and reduces significant CAPEX for larger networks. This architecture also provides network resiliency against LC/TRx or module failure and bandwidth scalability to support future generation PON architectures without any service interruption. [ABSTRACT FROM AUTHOR]

This paper presents a resource management of an arrayed waveguide grating for the design of access network in terms of reconfigurable bandwidth allocation and energy efficient operation. Power consumption characteristics of different channel routing mechanisms are investigated for the downstream transmission. Take-up rates of the subscribers are analyzed to estimate the required optical devices at different phases of the system. Traffic mode operation is also considered to realize the power reduction and energy efficiency for different channel routing mechanisms by the optimal use of components with respect to the active users. Proposed mechanisms are discussed in details and simulation results are presented for the energy savings on network scenario. The model which exploits free spectral range wrapping, has the most promising cost efficient device utilization, power consumption of 285 W and a minimum of 45% energy saving characteristics as compared to the conventional model. [ABSTRACT FROM AUTHOR]

We propose an efficient energy-saving scheme by dividing the optical network units (ONUs) into groups composed of one master-ONU (M-ONU) and several slave-ONUs (S-ONUs). The S-ONUs are primarily selected to communicate with the M-ONU and, second, with the remote node (RN), which can reduce the usage of high-power ports at the RN and subsequently decrease energy consumption. It is demonstrated that obvious energy-saving effects can be achieved, and moreover, the energy-saving efficiency can be further improved by expanding the capacity of the links between RN and M-ONUs and properly selecting the scale of the ONU group.

We proposed and experimentally demonstrated a wavelength-space division multiplexing (WSDM) optical access network architecture with centralized optical carrier delivery utilizing multicore fibers (MCFs) and adaptive modulation based on reflective semiconductor amplifier (RSOA). In our experiment, five of the outer cores are used for undirectional downstream (DS) transmission only, whereas the remaining outer core is utilized as a dedicated channel to transmit upstream (US) signals. Optical carriers for US are delivered from the optical line terminal (OLT) to the optical network unit (ONU) via the inner core and then transmitted back to the OLT after amplification and modulation by the RSOA in the colorless ONU side. The mobile backhaul (MB) service is also supported by the inner core. Wavelengths used in US transmission should be different from that of the MB in order to avoid the Rayleigh backscattering effect in bidirectional transmission. With quadrature phase-shift keying--orthogonal frequency-division multiplexing (QPSK-OFDM) modulation format, the aggregation DS capacity reaches 250 Gb/s using five outer cores and ten wavelengths, and it can be further scaled to 1 Tb/s using 20 wavelengths modulated with 16 QAM-OFDM. For US transmission, 2.5 Gb/s QPSK-OFDM transmission can be achieved just using a low-bandwidth RSOA, and adaptive modulation is applied to the RSOA to further enhance the US data rate to 3.12 Gb/s. As an emulation of high-speed MB transmission, 48 Gb/s in-phase and quadrature (IQ) modulated popularization division multiplexing (PDM)-QPSK signal is transmitted in the inner core of MCF and coherently detected in the OLT side. Both DS and US optical signals exhibit acceptable performance with sufficient power budget.

This paper reviews various energy efficient approaches in existence and proposes a Hybrid WDM-TDM PON architecture that allows the adaptive bandwidth allocation mechanism to reduce central office power consumption with acceptable performance. Our proposed architecture allows sending two signals, one broadband and other narrowband to each optical networking unit so an appropriate signal can be utilized according to the traffic demand. In case of very low traffic, only narrowband signal is used and a significant amount of energy consumption and OPEX is reduced. By using $$2\times \hbox {N}$$ power splitter and interleaver, proposed architecture provides broadcasting at both broadband and narrowband signal depending on the required link rate. This further reduces energy consumption and OPEX by avoiding the transmission of same signal from multiple sources. Offered data rates to the optical distribution networks (ODNs) may also be varied by doubling the wavelength spacing of remote node AWG so that two contiguous wavelengths can be transmitted at each port or ODN. This provides the geographical dynamic bandwidth allocation. Proposed architecture also support simultaneous transmission of both broadband and narrowband signals to the ODN to provide bandwidth scalability and network extensibility for supporting future access network in terms of new users and data rates. As two signals are reaching to any ODN, resiliency against OLT TRx and line card failure is also achieved. The performance of the proposed design is verified by simulation results in terms of bit error rate and receiver sensitivity to demonstrate its feasibility for the next-generation optical access network. [ABSTRACT FROM AUTHOR]

With the increase in varieties of services in network, time-sensitive services (TSSs) appear and bring forward an impending need for delay performance. Ultralow-latency communication has become one of the important development goals for many scenarios in the coming 5G era (e.g., robotics and driverless cars). However, the conventional methods, which decrease delay by promoting the available resources and the network transmission speed, have limited effect; a new breakthrough for ultralow-latency communication is necessary. We propose a de-optical-line-terminal (De-OLT) hybrid access–aggregation optical network (DAON) for TSS based on software-defined networking (SDN) orchestration. In this network, low-latency all-optical communication based on optical burst switching can be achieved by removing OLT. For supporting this network and guaranteeing the quality of service for TSSs, we design SDN-driven control method and service provision method. Numerical results demonstrate the proposed DAON promotes network service efficiency and avoids traffic congestion. [ABSTRACT FROM AUTHOR]

We propose a flexible and reconfigurable wavelength-division multiplexing (WDM) multicast scheme supporting downstream emergency multicast communication for WDM optical access network (WDM-OAN) via a multicast module (MM) based on four-wave mixing (FWM) in a semiconductor optical amplifier. It serves as an emergency measure to dispose of the burst, large bandwidth, and real-time multicast service with fast service provisioning and high resource efficiency. It also plays the role of physical backup in cases of big data migration or network disaster caused by invalid lasers or modulator failures. It provides convenient and reliable multicast service and emergency protection for WDM-OAN without modifying WDM-OAN structure. The strategies of an MM setting at the optical line terminal and remote node are discussed to apply this scheme to passive optical networks and active optical networks, respectively. Utilizing the proposed scheme, we demonstrate a proof-of-concept experiment in which one-to-six/eight 10-Gbps nonreturn-to-zero-differential phase-shift keying WDM multicasts in both strategies are successfully transmitted over single-mode fiber of 20.2 km. One-to-many reconfigurable WDM multicasts dealing with higher data rate and other modulation formats of multicast service are possible through the proposed scheme. It can be applied to different WDM access technologies, e.g., time-wavelength- division multiplexing-OAN and coherent WDM-OAN, and upgraded smoothly. [ABSTRACT FROM AUTHOR]

We investigate the transmission performance of 28-Gb/s nonreturn-to-zero on-off keying (NRZ-OOK), duobinary, and four-level pulse amplitude modulation signals over different fiber lengths without any inline amplification or pre/ post-processing digital signal processing technique by utilizing an O-band 18G-class directly modulated laser (DML). By experiment, it is verified that negligible sensitivity penalty is introduced by DML chirp effect after fiber transmission, which is due to the extremely low dispersion of O-band wavelengths. Meanwhile, the results indicate that NRZ-OOK outperforms the other two formats in receiver sensitivity, and for 20-km transmission, a power budget of 25.5 dB is achieved without pre-amplification. According to the experimental results, O-band DML-based NRZ-OOK transmission is a cost-effective solution for future 100G-EPON. [ABSTRACT FROM PUBLISHER]

Ubiquitous data center optical interconnection between user and data center has become a promising scenario gradually to accommodate high-performance services with end-to-end quality guaranteed. In our previous work, we implemented to provision data center application in inter-data center optical interconnection. In view of this, this study extends to consider the networking relationship between user and data center. We propose a novel software-defined clustered-optical access networking (SD-COAN) architecture for data center services in ubiquitous data center optical interconnection. A cross-stratum flow schedule (CSFS) strategy is introduced for SD-COAN based on the proposed architecture. The SD-COAN can enhance the responsiveness to the dynamic end-to-end data center demands and globally optimize optical access network and application resources effectively. The overall feasibility and efficiency of the proposed architecture are experimentally verified on our OpenFlow-based enhanced SDN testbed. The performance of CSFS strategy under heavy traffic load scenario is also quantitatively evaluated based on SD-COAN architecture in terms of resource occupation rate, average throughput and average provisioning delay, compared with other provisioning strategy. [ABSTRACT FROM AUTHOR]

It is important to economize the infrastructure of the access network and enhance its profitability because it represents the greatest part of network infrastructure cost. As 10G-EPON can be cost-effectively shared among various access services, it is one of the strong candidates to reduce the infrastructure cost of the next-generation access network. To further enhance cost effectiveness, it is useful to improve the acceptable link budget of access systems by using optical amplifiers (OAs), which can increase the splitting ratios and extend the reachable distance of the system. In this paper, we demonstrate an $N$:1 redundant 10G-EPON system with dual-rate central-office-set-type semiconductor optical amplifier (CO-SOA). Our 10G-EPON system reduces OPEX and CAPEX due to its extended reachable distance and elimination of intermediate offices while keeping its system reliability with the $N$ :1 protection system. Moreover, we also develop a method for estimating the total reachable distance of 10G-EPON systems with OAs in order to quantitatively evaluate the effect of extending reachable distance on various combinations of splitting ratio based on the results of actual demonstrations. Analyses of field measurement results clarify that the proposed system has sufficient design flexibility so as to satisfy the subscriber distribution requirements as regards the factors of splitting ratio and reachable distance. The results indicate that the $N$:1 optical subscriber unit protection with CO-SOAs is a promising approach to practical 10G-EPON systems that are cost effective and reliable. [ABSTRACT FROM PUBLISHER]

In this paper, we propose an auto-configurable optical amplifier (AC-OA) for passive optical networks (PONs); the value of optical attenuation is automatically controlled to prevent optical overloading of the OA. The AC-OA has a variable optical attenuator (VOA) at the input and a controller synchronized with an external facility database (FDB). The controller obtains the infrastructure information of each ONU and calculates the optimum setting for the input VOA. This structure enables the AC-OA to autonomously react to the spectrum being used. We simulate AC-OA operation based on the parameters of a commercial access network and evaluate the installation-cost reduction possible. [ABSTRACT FROM PUBLISHER]

A flexible hybrid wavelength division multiplexing-time division multiplexing passive optical network architecture that allows dual rate signals to be sent at 1 and 10 Gbps to each optical networking unit depending upon the traffic load is proposed. The proposed design allows dynamic wavelength allocation with pay-as-yougrow deployment capability. This architecture is capable of providing up to 40 Gbps of equal data rates to all optical distribution networks (ODNs) and up to 70 Gbps of a asymmetrical data rate to the specific ODN. The proposed design handles broadcasting capability with simultaneous point-to-point transmission, which further reduces energy consumption. In this architecture, each module sends a wavelength to each ODN, thus making the architecture fully flexible; this flexibility allows network providers to use only required OLT components and switch off others. The design is also reliable to any module or TRx failure and provides services without any service disruption. Dynamic wavelength allocation and pay-as-you-grow deployment support network extensibility and bandwidth scalability to handle future generation access networks. [ABSTRACT FROM AUTHOR]

According to the energy consumption status and network characteristics of the optical access network，the energy consumption distribution and the main factors that could affect energy consumption in optical access network environment were analyzed. Based on the analysis，energy-saving method of equipments and new technology of energy-saving and optical access network were researched，and then，laboratory test was developed. All of these could provide credible theory and experience for green optical access network application.

Context: Growth in bandwidth demand has boosted the development of new techniques for the transmission of information in telecommunication networks. Passive Optical Networks (PON) are presented as an alternative to conventional networks based on copper. This paper proposes and assesses the performance of an optical access network with TDM-WDM and wired-wireless convergence. Method: A teletraffic study was performed using a discrete event simulator. A simulation scenario was set up in order to obtain the packet loss and throughput of an optical access network under different load values, percentage of ONUs demanded bandwidth and number of wavelengths. Results: As the number of wavelengths used to cope with the exceeding traffic demanded by users, the results show that packet loss tends to decrease and throughput tends to increase in the network. Conclusions: The behavior of the variables analyzed in the results shows that when dimensioning a channel wavelength, which is required to determine the amount of resources needed to meet the bandwidth demand of the users, the proposed model positively influences the network behavior.