An upgradeable WDM-PON for broadcast and LAN services

We present a novel Wavelength-division-multiplexed passive optical network (WDM-PON) architecture for broadcast and local area network (LAN) services. The virtual ring LAN in the system can be utilized to not only realize LAN services but also provide broadcast services and extra point-to-point (P2P) bandwidth for optical network units (ONUs). A simulation study is performed to demonstrate this scheme. Its result indicates the LAN signals achieve optimum performance when extinction ratio (ER) is 4 dB.     

Self-protected ring-star-architecture TDM passive optical network with triple-play management

A new self-protected apparatus in ring-star-architecture for time division multiplexed passive optical network (TDM-PON) against fiber-fault; together with triple-play management in optical layer is proposed and investigated. Different scenarios of fiber-fault locations are also discussed and analyzed. Besides, the performance of data traffics in both uplink and downlink directions are also measured and studied. Standard CATV video signal distribution to each ONUs is also performed, showing the proposed access network cannot only have self-restored function, but also can manage triple-play services in the optical layer.     

Fiber-fault protection WDM-PON using new apparatus in optical networking unit

In this study, we propose and experimentally demonstrate a simple self-protection architecture for WDM passive optical network (PON) by adding a novel 2 × 2 optical switch design in each optical networking unit (ONU). Two adjacent ONUs are interconnected into a group. By using the proposed protection architecture, the affected traffic can be restored immediately against fiber fault in the feeder and distributed fibers. Moreover, the performance of proposed self-protection WDM-PON is also discussed and analyzed.     

Investigation on wavelength re-modulated bi-directional passive optical network for different modulation formats

In this paper, the cost effective bi-directional passive optical network architecture with wavelength remodulated scheme is investigated. To realize the cost-effective PON, remodulation scheme is used, in which the downstream optical signal is reused as a carrier for the upstream transmission as it eliminates the need for an extra laser source at optical network units. The performance of proposed passive optical network is analyzed and compared for various modulation formats such as Non Return to Zero (NRZ), Return to Zero (RZ) and On–Off Keying (OOK) with 64 optical networks units (ONUs) at different traffic speed for downlink and uplink, respectively. It has been observed that the most suitable data format for proposed PON network is NRZ. Further the proposed system performance is compared with the current state-of-the-art PON architectures.     

Survivable WDM-PON with self-protection and in-service fault localization capabilities

In this paper, we analyze the survivability of wavelength division multiplexed (WDM) passive optical network (PON). We propose and experimentally demonstrate a novel survivable WDM-PON architecture with self-protection and in-service fault localization capabilities. Two WDM-PONs are combined together and multiple sub-ring architecture is formed. Protection switching is achieved automatically at optical network units (ONUs) when failure occurs. Fiber loss, fiber fault localization and automatic protection switching in each ONU are real-time monitored in central office (CO) without interrupting customer service. No signaling for failure notice or protection switching is required for either CO or ONUs. Extra fibers required for protection are minimized compared with previous protection schemes. The self-protection and in-service fault localization capabilities of the proposed WDM-PON architecture are experimentally verified.     

Collective reception of orthogonal band multiplexed data streams for OFDM-PON upstream transmissions

We propose and demonstrate a novel OFDM-PON upstream transmission architecture with traffic aggregation by orthogonal band multiplexing. The aggregated data streams that propagate in different fiber lengths from ONUs are collectively received and demodulated using one receiver, when the OFDM signals are in a synchronous state. In simulation, four optical network units (ONUs) transmit upstream data at four different frequency bands, and use orthogonal band multiplexing with a proper configuration. The orthogonal band multiplexed 10-Gb/s OFDM signal is collectively received to validate the feasibility of the architecture. We also conduct a proof-of-concept experiment to verify the orthogonal band multiplexing and collective reception. We also verify that the tolerance to the time mismatch of the orthogonal band multiplexing is twice of the CP length.     

Novel Quantum Virtual Private Network Scheme for PON via Quantum Secure Direct Communication

Two quantum secure direct communication (QSDC) protocols with quantum identification (QI) based on passive optical network (PON) architecture are proposed. One QSDC protocol can be implemented between two different optical network units just with simple configurations of PON by optical line terminal when they are in the same virtual private network after optical line terminal performing QI to the optical network units in the given PON architecture. The other QSDC protocol is also implemented between any two legitimated users in the virtual private network but with considerable reduction of workload of the optical line terminal. The security analysis shows that the proposed QSDC schemes with quantum identification are unconditionally secure and allow the legitimate users to exchange their secret information efficiently and to realize a quantum virtual private network in the PON networks ultimately.     

Adaptive dynamic bandwidth allocation algorithm supporting multi-services over Ethernet passive optical networks

In order to ensure fairness of each optical networks unit (ONU) in access network and meet quality of service (QoS) requirements of differentiated service such as voice, video and data, Ethernet passive optical network (EPON) dynamic bandwidth allocation (DBA) algorithm should avoid light load penalty, choose different scheduling scheme according to light loading or heavy loading circumstances, adaptively adjust the order of ONUs at the case heavy loading in order to guarantee QoS. Aiming at this problem, an adaptive dynamic bandwidth allocation algorithm supporting multi-services is presented. The algorithm guarantees QoS through dividing service into voice, video and data putting them into different queues, optical line terminal (OLT) collects all requests of different services from different ONUs, divides the adopted scheduling scheme according to loading, adaptively adjusts the order of ONUs queue based on minimum delay at the case heavy load. Therefore, it can really guarantee QoS. Simulation results of the algorithm show that the algorithm not only can support multi-service and avoid light load penalty, but also can guarantee the fairness of each ONUs and QoS. It has a better performance than other algorithms particularly at the case of heavy loading.     

A long-reach WDM passive optical network enabling broadcasting service with centralized light source

We propose a long-reach wavelength-division-multiplexed (WDM) passive optical network (PON) to provide conventional point-to-point (P2P) data and downstream broadcasting service simultaneously by superimposing, for each WDM channel, the differential-phase-shift-keying (DPSK) broadcasting signal with the subcarrier multiplexing (SCM) modulated downstream P2P signal, at the optical line terminal (OLT). In the optical network units (ONUs), by re-modulating part of the downstream signal with a reflective semiconductor optical amplifier (RSOA), we realize color-less ONUs for upstream data transmission. The proposed scheme is numerically verified with a 5 Gb/s downstream P2P signal and broadcasting services, as well as 2.5 Gb/s upstream data through a 60 km bidirectional fiber link. In particular, the influence of the downstream lightwave's optical carrier–subcarrier ratio (OCSR) on the system performance is also investigated.     

OFDMA-based LAN emulation in long-reach hybrid PON system

A novel long-reach, hybrid wavelength-division multiplexing (WDM) and time-division multiplexing (TDM) passive optical network (PON) architecture which supports local area network (LAN) emulation among customers is proposed. Orthogonal frequency division multiplexing access (OFDMA) technology is used in optical network units (ONUs) to transmit the LAN data. The optical LAN data from an ONU is converted into the electrical signal and combined with TDM downstream access data in the extended box for delivery to other ONUs. This scheme has many advantages on LAN emulation, such as dynamic allocation of LAN bandwidth, no bandwidth cost of TDM business, supporting multiple concurrent LAN services and so on. Simulations are performed to verify the scheme. Tolerance of dispersion and factors that influence the performance of various independent services are all investigated and analyzed.     

Ring-based PON supporting multiple optical private networks using OCDMA technique

This work is a novel attempt to provide local communications for multiple optical private networks (PNs) within ring-based passive optical network (PON). In order to improve network throughput performance, PNs traffic is decentralized from PON traffic let no extra traffic management into optical line terminal (OLT). To achieve multiple secure optical private networking over ring-based PON layout, optical code division multiple access (OCDMA) technique is applied. This technique leads to interconnect optical network units (ONUs) in the same PN sharing the same codeword while other PNs benefiting from different codewords. This scheme can be used in access networks to establish discrete communications between different sites in an enterprise or a university campus or even a residential accommodation. The proposed network architecture is then set up and its bit error rate performance is experimentally demonstrated. Finally, the network scalability and throughput performance of the proposed scheme are analyzed.     

Analysis of Transmission Performance in SUPERPONs

In this work we study how optical amplifiers can deeply improve the performance of the passive optical networks (PONs), permitting a large number of optical network units (ONUs), transmitting at high bit rate. These high-capacity networks are called SUPERPONs, and we show how to achieve a network with 8,192 ONUs with a transmission in the downstream direction up to 10 Gbit/s.     

Analysis of Transmission Performance in SUPERPONs

In this work we study how optical amplifiers can deeply improve the performance of the passive optical networks (PONs), permitting a large number of optical network units (ONUs), transmitting at high bit rate. These high-capacity networks are called SUPERPONs, and we show how to achieve a network with 8,192 ONUs with a transmission in the downstream direction up to 10 Gbit/s.     

Twin-Ring Optical WDM-MAN Enabling Triple-Hierarchical Reconfigurations and Quadruple-Shared Protections

An optical wavelength division multiplexing metro access network is proposed in this paper. With the design of flexible distribution node (FDN), three kinds of reconfigurable networks can be flexibly built to achieve intra- and inter-optical network unit (ONU)-direct communications. With the adoption of multiple tangent twin-ring topologies, four-level shared protections covering both feeder and distribution fibers are also supported. Moreover, the network can be smoothly expanded by adding express ONUs connected to FDNs. Thus, the network can not only achieve capacity increasing but also support full-duplex reconfigurable communication. A reconfigurable transmission algorithm is also set to avoid wavelengths conflict.     

Performance evaluation of bi-directional passive optical networks in the scenario of triple play service

In this paper, the performance of bi-directional passive optical network (BPON) has been evaluated and compared at different bit rates in the scenario of triple play service. The triple-play service is realized as a combination of data, voice and video signals. This architecture is investigated for symmetrical data traffic for uplink and downlink transmission and its performance is also evaluated in terms of Q-factor and eye height at different transmission distance. The Q-factor results show the acceptable performance at 10 Gbps data rate for downstream and upstream transmission, as it accommodates 128 optical network units (ONUs). Further the proposed system's performance is compared with the current state-of-the-art PON architectures.     

Adaptive upstream rate adjustment by RSOA-ONU depending on different injection power of seeding light in standard-reach and long-reach PON systems

The wavelength division multiplexing-time division multiplexing (WDM-TDM) passive optical network (PON) using reflective semiconductor optical amplifier (RSOA)-based colorless optical networking units (ONUs) is considered as a promising candidate for the realization of fiber-to-the-home (FTTH). And this architecture is actively considered by Industrial Technology Research Institute (ITRI) for the realization of FTTH in Taiwan. However, different fiber distances and optical components would introduce different power budgets to different ONUs in the PON. Besides, due to the aging of optical transmitter (Tx), the power decay of the distributed optical carrier from the central office (CO) could also reduce the injection power into each ONU. The situation will be more severe in the long-reach (LR) PON, which is considered as an option for the future access. In this work, we investigate a WDM-TDM PON using RSOA-based ONU for upstream data rate adjustment depending on different continuous wave (CW) injection powers. Both standard-reach (25 km) and LR (100 km) transmissions are evaluated. Moreover, a detail analysis of the upstream signal bit-error rate (BER) performances at different injection powers, upstream data rates, PON split-ratios under stand-reach and long-reach is presented.     

50 km bidirectional FTTH transmission comparing different PON standards

In this paper, a bidirectional Fiber To The Home (FTTH) is proposed where WDM transmitter is used as a seeding source with wavelength of 1550 nm. The system utilizes a Travelling wave Semiconductor Optical Amplifier (TSOA) with injection current 0.15A. 50 km range FTTH architecture is demonstrated for both downstream and upstream channels. We investigated the impact of different data rates on upstream and downstream data. The BER results show that the performance of our scheme is good for 10 Gbps system for downstream transmission as it accommodates 64 ONUs. From simulation results show the BER of 9.95e-009 is reported at 15 Gbps but only in case of 32 ONUs. Similarly, in case of upstream transmission, Q-Factor of 15.04 dB is reported for 32 ONUs. So this scheme is a practical solution to meet the data rate of the optical links simultaneously in tomorrow's PON access networks.     

Self-healing ring-based WDM-PON

In this paper, a survivable ring-based wavelength-division-multiplexing (WDM)-passive optical network (PON) for fiber protection is proposed. Protections for feeder fiber and distributed fiber are independent in the scheme. Optical line terminal (OLT) and optical network units (ONUs) can automatically switch to protection link when fiber failure occurs. Protection distributed fiber is not required in the scheme. Cost-effective components are used in ONUs to minimize costs of network. A simulation study is performed to demonstrate the scheme. Its result shows good performance of upstream and downstream signals.     

光互连网络中四功能交换开关研究

由节点开关单元按照一定的连接规则所构成的光互连网络,在全光通信和光信息处理中具有重要的应用。基于节点开关一般实现光信号的直通和交换功能的特点,利用成熟的偏振光控制技术,通过位相型空间光调制器对信号光偏振态的控制,完成信号的路由和开关动作,从而设计出具有直通、交换、上播和下播功能的节点交换开关。与传统设计思想相比,该方法不仅能够充分利用信号光的能量,有效的减少光能量的损耗,而且还具有与偏振无关等特点。该四功能交换开关,对于优化和拓展光互连网络的结构和功能具有一定的意义。     

A cost-effective WDM-PON architecture simultaneously supporting wired, wireless and optical VPN services

It is believed that next-generation passive optical networks (PONs) are required to provide flexible and various services to users in a cost-effective way. To address this issue, for the first time, this paper proposes and demonstrates a novel wavelength-division-multiplexed PON (WDM-PON) architecture to simultaneously support three types of services: 1) wireless access traffic, 2) optical virtual passive network (VPN) communications, and 3) conventional wired services. In the optical line terminal (OLT), we use two cascaded Mach-Zehnder modulators (MZMs) on each wavelength channel to generate an optical carrier, and produce the wireless and the downstream traffic using the orthogonal modulation technique. In each optical network unit (ONU), the obtained optical carrier is modulated by a single MZM to provide the VPN and upstream communications. Consequently, the light sources in the ONUs are saved and the system cost is reduced. The feasibility of our proposal is experimentally and numerically verified.