Fiber-wireless (FiWi) access network: Performance evaluation and scalability analysis of the physical layer

The fiber-wireless (FiWi) access network is a prestigious architecture for next generation (NG) access network. NG access networks are proposed to provide high data rate, broadband multiple services, scalable bandwidth, and flexible communication for manifold wireless end-users (WEUs). In this paper, the FiWi access network is designed based on a wavelengths division multiplexing/time division multiplexing passive optical network (WDM/TDM PON) at the optical backhaul with data rate of 2.5 Gb/s and wireless fidelity-worldwide interoperability for microwave access (WiFi–WiMAX) technologies at the wireless front-end along a 50 m–5 km wireless links with data rate of 54–30 Mb/s, respectively. The performance of the optical backhaul and the wireless front-end, in the proposed FiWi access network, has been evaluated in terms of bit error rate (BER), error vector magnitude (EVM), and signal-to-noise ratio (SNR) of the physical (PHY) layer. The scalability of the optical backhaul based on maximum split ratio of 1/32 for each wavelength channel and a fiber length of 24 km from the central office (CO) to the access point (AP) is analyzed with bit error rate (BER) of 10⁻⁹.     

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.     

Control packet signaling mechanism using electronic code division multiple access for packet-based networks

We propose and experimentally demonstrate the feasibility of a control packet signaling technique using electronic code division multiple access for a wavelength division multiplexing packet-based network, whereby each wavelength channel is assigned a unique electronic code based label on a radio frequency subcarrier. Such a technique allows each wavelength channel to be electronically identified without requiring the use of a WDM demultiplexer. We experimentally demonstrate this technique with two wavelength channels each with 1.25 Gb/s baseband payload data and 10 Mb/s header coded onto an electronic code at 160 Mb/s. A performance study of the electronic code division multiple access based control signaling scheme in a wavelength division multiplexed packet-based access network is also performed in terms of the required power budget to monitor the electronic code division multiple access control signals in the presence of several sources of noise for error-free transmission of both payload data and electronic code division multiple access based control signals. It is shown that the modulation depth of each signal impacts the amount of required optical tap power. As the modulation depth of the electronic code division multiple access based control signal is increased, the required optical tap power is reduced. However, this increases the bit-error-rate for the payload data. Therefore, there lies a maximum and a minimum of the required tap optical power for the successful recovery of both signals. The lower bound of this range is usually determined by the successful recovery of electronic code division multiple access based control signal while the upper bound is determined by the successful recovery of payload data. The required optical tap power is analyzed for different transmission bit rates of the payload data for various receiver architecture scenarios without an optical amplifier at the receiver. The scalability analyses were repeated with an optical amplifier placed in the receiver terminal of the network. The resulting optical tap power that is required for the successful monitoring of the electronic code division multiple access based control signals are compared with that of the case without the amplifier.     

Costs of Fiber-to-the-Home Passive Optical Network Unbundling

Abstract

This work considers different unbundling options for local loop unbundling in order to provide multi-operator access and consider the economical impact for the fiber-to-the-home next-generation access entrants to deploy such alternatives. It is shown that deploying wavelength division multiplexing networks is an efficient strategy to perform local loop unbundling while upgrading the gigabit passive optical network for the new era where high bandwidths are necessary for satisfying customer demand. In areas with a high population density, wavelength division multiplexing techniques are the most suitable for entrant operators to access the incumbent's network and provide service.     

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.     

Design and performance evaluation of a metro WDM storage area network with IP datagram support

Storage area networks (SANs) are becoming an important part of optical MANs (metropolitan area networks). Growing storage and business-continuity needs; high-bandwidth, low latency requirements for SANs; storage infrastructure consolidation; and post-9/11 regulatory issues are among the several driving factors to push this trend. We, in this paper, consider a metro wavelength division multiplexing (WDM) SAN that allows the transmission of variable packet size such as Internet protocol (IP) datagram and evaluate its performance by means of discrete-event simulation. The network is based on one fixed transmitter and multiple fixed receivers. Beginning with an introduction and the context of this work, we describe the network and node architectures; and introduce the medium access control (MAC) protocols. Subsequently, using the Poisson and self-similar traffic, we present and discuss performance of the proposed network architecture in terms of throughput and queuing delay under symmetric and asymmetric traffic scenarios. The simulation results suggested that the proposed architecture is suitable for SAN applications which demand low queuing delay and high throughput.     

Absolute polar duty cycle division multiplexing over wavelength division multiplexing system

The performance of absolute polar duty cycle division multiplexing (AP-DCDM) over wavelength division multiplexing (WDM) system is presented based on the simulation results. The AP-DCDM signal has narrower bandwidth than conventional time division multiplexing (TDM) signal, which makes its implementation in WDM system advantageous. In this paper, characteristics of AP-DCDM and TDM signals in WDM system are compared at the speed of 40 Gbit/s per channel, for the minimum allowed channel spacing and the chromatic dispersion tolerance. The results clearly show that AP-DCDM performs significantly better than TDM. By using AP-DCDM, 1.28 Tbit/s (32 × 40 Gbit/s) was successfully transmitted over 320 km standard single mode fiber. Spectral efficiency of 0.64 b/s/Hz was achieved by using 10 Gbit/s transmitters and receivers without polarization multiplexing.     

A Survivable Wavelength Division Multiplexing Passive Optical Network with Both Point-to-Point Service and Broadcast Service Delivery

Abstract

A survivable wavelength division multiplexing passive optical network enabling both point-to-point service and broadcast service is presented and demonstrated. This architecture provides an automatic traffic recovery against feeder and distribution fiber link failure, respectively. In addition, it also simplifies the protection design for multiple services transmission in wavelength division multiplexing passive optical networks.     

面向LOFAR应用的160Gbit/s OTDM试验平台

报告了一个用于低频射频天线网络LOFAR的160 Gbit/s 演示平台.文章介绍了LOFAR网络结构以及用于LOFAR长臂的OTDM/WDM系统结构,回顾并探讨了用于实现160 Gbit/s系统的关键技术,并介绍了实验室中实现该160 Gbit/s OTDM/WDM演示平台所采用的技术方案。出于经济性考虑,所有的关键系统功能都采用自己搭建方案.     

Optimal design of 32 channels spectrum slicing WDM for optical fiber access network system

In this article, the spectrum sliced dense wavelength division multiplexed passive optical network (SS-DWDM–PON) has been investigated as a power efficient and cost effective solution for optical access networks. In this work an AWG demultiplexer is used to operate as slicing system. The high speed SS-DWDM system has been realized and investigated for 32 channels with data rate up to 3 Gb/s using broadband ASE source (LED). The 3 Gb/s signals both non-return-to-zero (NRZ) and return-to-zero (RZ) were demonstrated in 40 km optical fiber link with BER < 10⁻¹². The results obtained here demonstrate that SS-DWDM is well suited for Fiber-to-the-Home (FTTH) network.     

Spectral efficient hybrid wireless optical broadband access network (WOBAN) based on transmission of wireless MIMO OFDM signals over WDM PON

In this paper, a spectral efficient hybrid wireless optical broadband access network (WOBAN) is proposed and demonstrated based on the transmission of wireless multi-input multi-output orthogonal frequency division multiplexing (MIMO OFDM) signals over wavelength division multiplexing passive optical network (WDM PON). By using radio over fiber (ROF) techniques, the optical fiber is well adapted to propagate multiple wireless services having different carrier frequencies. It is a known fact that multiple wireless signals having the same carrier frequency cannot propagate over a single optical fiber at the same time, such as MIMO signals feeding multiple antennas in fiber wireless (FiWi) system. A novel optical single-sideband frequency translation technique is designed and simulated to solve this problem. This technique allows four pairs of wireless MIMO OFDM signals with the same carrier frequency for each pair to be transmitted over a single optical fiber by using one optical source per wavelength. The crosstalk between the different MIMO channels with the same frequency is eliminated, since each channel is upconverted on specified wavelength with enough channel spacing between them. Also the maximum crosstalk level between the different MIMO channels with different frequencies is very low around ?76 dB. The physical layer performance of the proposed WOBAN is analyzed in terms of the bit error rate (BER), error vector magnitude (EVM), and signal-to-noise ratio (SNR). The proposed WOBAN achieves 7.68 Gb/s data rate for 20 km for the optical back-end and 240 Mb/s for the outdoor wireless front-end.     

Enhanced performance for 10 Gb/s long reach RSOA based WDM-PON by using power pre-emphasized OFDM signal

An extended reach 10 Gb/s wavelength division multiplexing passive optical networks (WDM-PONs) system based on reflective semiconductor optical amplifier (RSOA) is proposed by using power pre-emphasized orthogonal frequency division multiplexing (OFDM) signal. Experimental results show that the proposed technique can effectively enhance the system performance against the limited bandwidth and chirp induced fading effect from direct modulation of RSOA. The receiver sensitivity is improved by 5 dB at the limit of BER for forward error correction (FEC) code over the 60 km and 85 km fiber transmission without any dispersion compensation module.     

A novel full duplex 16 Gbps SCM/ASK radio over fiber WDM-PON sharing wavelength for up- and down-link using bidirectional reflective filter

In this paper, a new bidirectional wavelength division multiplexing radio-over-fiber (WDM-RoF) using Subcarrier Multiplexing/Amplitude Shift Keying (SCM/ASK) is proposed which shares the same wavelengths for both up-link and down-link. A bidirectional reflective filter (BRF) is utilized in the upstream link to provide a reliable bidirectional optical channel. WDM is used to further increase the capacity of system. Simulation of the proposed scheme demonstrates 1 Gbps down- and up-link data stream for 16 channels over the length of 25 km with acceptable Q-factor (>6 dB).     

Hybrid WDMA/OCDM system with the capability of encoding multiple wavelength channels by employing one encoder and one corresponding optical code

<正>A hybrid wavelength division multiple access(WDMA)/optical code division multiplexing(OCDM) system is proposed,where the optical code is not the same as the address of every optical network unit(ONU); rather,the code is a virtual fiber of hybrid passive optical network(PON).To our knowledge,this is the first report analyzing a single encoder/decoder with a single corresponding optical code being exploited to encode/decode multiple wavelength signals simultaneously.This system enables OCDM to become transparent to ONU so that the existing wavelength division multiplexing(WDM) PON can be upgraded. Thus,redesigning the optical line terminal and ONU can be easily accomplished,and greatly decreasing the number of encoder/decoder becomes possible.In experiment,we only employ two encoder/decoder pairs to combine two WDM-PONs in one fiber.Simulation results confirm the feasibility of the proposed system.     

A Wavelength and Bandwidth Assignment Algorithm to Support Guaranteed Bandwidth Levels in Hybrid Time Division Multiplexing/Wavelength Division Multiplexing Ethernet Passive Optical Networks

Abstract

A novel bandwidth assignment algorithm in wavelength division multiplexing Ethernet passive optical networks, called a dynamic wavelength assignment service level agreement, is proposed to efficiently provide subscriber differentiation. Simulation results show that the dynamic wavelength assignment service level agreement outperforms other bandwidth allocation algorithms in wavelength division multiplexing Ethernet passive optical networks, as it makes a fairer bandwidth distribution than other methods and is able to overcome the non-allowed packet fragmentation of the Ethernet passive optical network standard. Consequently, it greatly increases the achieved throughput and always ensures a minimum guaranteed bandwidth to every priority subscriber. Furthermore, the new algorithm obtains lower mean packet delay and packet loss rate for the highest priority subscribers when compared with other bandwidth distribution schemes in wavelength division multiplexing Ethernet passive optical networks.     

A cost-effective structure of a centralized-light-source WDM-PON utilizing inverse-duobinary-RZ downstream and DPSK upstream

In this paper, we propose a new structure of a centralized-light-source wavelength division multiplexed passive optical network (WDM-PON) utilizing inverse-duobinary-return-to-zero (inverse-duobinary-RZ) downstream and DPSK upstream. It reuses downstream light for the upstream modulation, which retrenches lasers assembled at each optical network unit (ONU), and ultimately cuts down the cost of ONUs a great deal. Meanwhile, a 50-km-reach WDM-PON experiment with 10-Gb/s inverse-duobinary-RZ downstream and 6-Gb/s DPSK upstream is demonstrated here. It is revealed to be a novel cost-effective alternative for the next generation access network.     

Experimental demonstration of polarization multiplexing for simultaneously providing broadband wireless and wired access

A fiber-based wavelength-division-multiplexing (WDM) network utilizing polarization multiplexing (PolMUX) is proposed to simultaneously provide broadband wireless and wired services. In such a dual-service access network, the wireless and wired services are separately delivered in two orthogonal states of polarization with well independence in a single WDM channel. The impact of several polarization-dependent interferences becomes insignificant due to the relatively short transmission distance in access networks. The feasibility of PolMUX is experimentally demonstrated with a power penalty at BER = 10^-9 of about 0.5 dB and 1 dB for 2.5 Gb/s wired and wireless downstream services, respectively. The proposed system is compatible with the current reported techniques in either WDM passive optical networks (WDM-PON) or radio-over-fiber (ROF) systems.     

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.     

Transmission of 4× 40/10 Gbps in a WDM-PON using NRZ-DQPSK/ASK modulation

In this paper we demonstrate the feasibility to deploy a wavelength division multiplexing passive optical network (WDM-PON) of a 30 km standard single-mode fiber (SSMF-28) carrying 160 Gbps data in downstream and 40 Gbps through the uplink. The developed method is based on the comparison between two WDM-PON systems of 4 channels with the same characteristics, using two different formats of modulation in OLTs. The first system uses the NRZ-ASK in the downlink direction, while the second uses the NRZ-DQPSK.     

Advanced modulation formats for delivery of heterogeneous wired and wireless access networks

It is believed that the integration of wired and wireless access networks (or heterogeneous network) will provide high bandwidth and flexibility for both fixed and mobile users in a single and cost-effective platform. Here, we propose and demonstrate a signal remodulated wired and wireless network with wireless signal broadcast. Dark-return-to-zero (DRZ) and polarization-shift-keying (PolSK) signals are used for the downstream wired and wireless applications respectively. At the remote antenna unit (RAU), the PolSK signal is demodulated to produce the binary-phase-shift-keying (BPSK) signal, which will be used for the wireless broadcast application. Signal remodulation is demonstrated using reflective semiconductor optical amplifier (RSOA) as a colorless reflective modulator in the optical networking unit (ONU)/RAU. The downstream signal is remodulated at the ONU/RAU to produce the non-return-to-zero (NRZ) upstream signal.