KEYWORDS: Orthogonal frequency division multiplexing, Distortion, Radio over Fiber, Modulation, Modulators, Mathematical modeling, Signal to noise ratio, Nonlinear optics, Radio optics, Interference (communication)
This paper is concerned with the effect of the nonlinearity of an MZM (Mach-Zehnder modulator) on optical OFDM
signal distortion. The optical OFDM signal output from the MZM is expressed as a Taylor series including third-order
and fifth-order nonlinear distortion terms, by which we can easily establish a mathematical model of the optical OFDM
signals in different formats and rates. According to the model, we can get the EVM at the optimized point. Moreover, the
proposed theoretical model is proved in good agreement with experiment results of the RoF (Radio over Fiber) system.
KEYWORDS: Orthogonal frequency division multiplexing, Modulation, Optical amplifiers, Modulators, Phase modulation, Signal attenuation, Roads, Telecommunications, Radio over Fiber, Fiber optics
The OFDM-based mm-RoF technique emerges the possibility of cost-effective and high data rate
ubiquitous wireless networks. However, due to the existence of the nonlinear effects, the performance of
OFDM-based mm-RoF meets the limitations. In this paper we analyses the improved performance of a
16QAM-OFDM mm-RoF with predistortion design.
The influence of higher-order harmonics produced in modulator on flat and stable optical comb generation based on recirculating
frequency shifter (RFS) for all-optical OFDM is analyzed and demonstrated in this paper. We also
theoretically analyze the condition for flatness of the optical frequency comb. The resulting theoretical analysis is
confirmed by a 16 comb lines and 12.5 GHz spacing RFS generation system. The results demonstrate that flat and stable
optical comb generation based on RFS can be a useful solution for multi-wavelength source in all-optical OFDM.
In this paper, a numerical investigation on the nonlinear distortion of OFDM (Orthogonal Frequency Division
Multiplexed) signals caused by RSOA (Reflective Semiconductor Optical Amplifier) as an intensity modulator in
OFDM-PON system is undertaken. Based on curve fitting approach a fourth order polynomial is, for the first time, used
to present the nonlinear gain of RSOA. The expression of in-band and adjacent-band noise due to nonlinear distortion is
then derived. Besides, the EVM of system versus input signal power is simulated by VPItransmissionmaker7.6, the
results indicate the nonlinear effects-induced degradation of transmission performance depends highly on the third order
term of nonlinear distortion power, and the optimum input signal power is provided to improve the transmission
performance. Finally, it's worth mentioning that the quantified analysis method is applicable for the nonlinearity analysis
of any RSOA-Based OFDM-PON system.
This paper is dealing with the non-linear distortion of different optical modulators including directly modulated laser
diode (LD), Mach-Zehnder modulator (MZM) and reflective semi-conductor optical amplifier (RSOA), which are
candidates of optical device used to make colorless ONUs. To analyze the performance of different optical modulators a
unified mathematic model is developed in which the optical OFDM signal output from an optical modulator is expressed
as a power series including 1-st order and higher order terms. Based on this statistical model, the performance of the
modulators are computed and compared. The effect of third order distortion in modulating signal on error vector
magnitude (EVM) is particularly evaluated for optimizing the fiber transmission link.
KEYWORDS: Orthogonal frequency division multiplexing, Radio optics, Modulators, Modulation, Radio over Fiber, Single mode fibers, Optical filters, Hybrid fiber radio, Extremely high frequency, Optical amplifiers
This paper introduces in detail a novel 40-GHz radio over fiber (RoF) system based on optical frequency multiplication
with up to 1.4Gbps 16QAM-OFDM wireless signal employing a Mach-Zehnder modulator with no optical filtering. And
also what is discovered as expected during the experiment --- the optimal driving power of the intensity modulator (IM)
to relieve high peak-to-average power ratio (PAPR) of OFDM signal on intensity modulator with an acceptable SNR.
KEYWORDS: Orthogonal frequency division multiplexing, Extremely high frequency, Radio optics, Modulators, Radio over Fiber, Signal detection, Optical amplifiers, Signal attenuation, Fiber amplifiers, Photodiodes
This Letter proposes a low-cost Optical Frequency Multiplication (OFM) scheme based on dual drive Mach-Zehnder
Modulator (DD-MZM) to generate 40-GHz millimeter-Wave (mmW) signals and 32Gbps 64QAM-OFDM signal at the center frequency of 35GHz occupying 5.6GHz bandwidth applied to Radio-over-Fiber (RoF) system. The optimal driving power of Intensity Modulator (IM) is also discovered to achieve the smallest EVM (Error Vector Magnitude) for
the RoF system.
KEYWORDS: Frequency combs, Modulators, Modulation, Optical filters, Signal to noise ratio, Optical amplifiers, Spectrum analysis, Frequency modulation, Signal attenuation, Bessel functions
The performance of the optical frequency comb generation based on the re-circulating frequency shifter has been
analyzed and demonstrated in this paper. We have theoretically analyzed the condition for flatness of the optical
frequency comb and the relative intensity noise influence. And the resulting performance analysis has been confirmed by
a successfully generated 16 comb lines, which are stable and flat with spacing 12.5 GHz.
This paper presents an overview on millimeter wave radio over fiber systems based on millimeter wave generation by
optical frequency multiplication (OFM). The disadvantage of original OFM technique is checked and a novel
bi-directional mm-RoF system based on new OFM technique using dual-drive MZM as high-order optical side-modes
generator is proposed in principle and experimentally verified by a bi-directional mm-RoF system which not only
produces 38 GHz information bearing signal in downstream, but also provides 40GHz local reference for
down-conversion of upstream signal. Finally the advantage of OFM technique in reducing fading effect of fiber
dispersion is theoretically proved.
KEYWORDS: Detection theory, Optical filters, Signal generators, Signal processing, Radio propagation, Radio over Fiber, Radio optics, Modulators, Modulation, Telecommunications
In order to generate a stable and pure 60GHz millimeter-wave signal, a periodically wavelength-swept lightwave signal over a limited wavelength range which center wavelength at 1310nm and frequency-swept rate up to 1GHz is an important component of the whole system. In this paper, we focus on three methods to yield the wanted periodically wavelength-swept lightwave signal, which are sinusoidal wavelength scan, triangular wavelength scan and saw-toothed wavelength scan. We analyze in theory the power characteristics and the spectrum characteristics of the 60GHz millimeter-wave signals relative to the different wavelength-swept lightwave signal generated by different wavelength-swept methods. Furthermore, we simulate the 60GHz radio-over-fiber transmission systems respectively with the three wavelength sweep methods and gain the results in agreement with the analysis in theory.
This paper investigates the survivable traffic grooming problem for optical mesh networks employing wavelength-division multiplexing (WDM). While the transmission rate of a wavelength channel is high, the bandwidth requirement of a typical connection request can vary from the full wavelength capacity down to subwavelength. To efficiently utilize network resources, subwavelength-granularity connections can be groomed onto direct optical transmission channels, or lightpaths. Meanwhile, the failure of a network element can cause the failure of several lightpaths, thereby leading to large data and revenue loss. Fault-management schemes such as protection are essential to survive such failures. Different low-speed connections may request different bandwidth granularities as well as different protection schemes. How to efficiently groom such low-speed connections while satisfying their protection requirements is the main focus of our investigation. The paper tackles the dynamic survivable traffic grooming problems in multifiber wavelength-routed optical networks by representing the network as a layered graph model. This graph multi layers, where each layer represents a specific wavelength. Each link in the layered graph has more than one fibers and an associated cost. We use a modified Dijkstra algorithm that has a reduced complexity due to the structure of the layered graph. Heuristic algorithms for fiber selection based on a well-designed link-cost metrics are proposed. The performance of various routing algorithms is evaluated through simulation studies.
KEYWORDS: Video, Video surveillance, Field programmable gate arrays, Head, Internet, Fiber to the x, Remote sensing, Network security, Computer security, Communication engineering
IP Video service has a substantial growth on the internet in the last few years, and this gives a golden opportunity to popularize FTTH. As the hope of FTTH, EPON meets the bandwidth requirement of high quality video service. Using a point-to-multipoint topology, EPON is easy to set up channels for broadcast video. However, if the video stream isn't handled correctly, broadcast storm will occur on the attached link. So a novel scheme of multicasting IP Video over
EPON is presented in this paper to solve this problem. It not only guarantees validity of filtering video stream, but also guarantees QoS and security of this service. In the first part of this paper, the key technologies of multicasting IP video over EPON are introduced. Then FPGA implementation of this scheme is described in detail. Finally security of IP video is discussed.
In this paper, we study the problem of dynamic survivable routing in optical networks with Shared Risk Link Groups (SRLG). Survivability and service continuity have been well recognized as the most important issues in the design of control and management planes for the next-generation optical networks with wavelength-division multiplexing (WDM) as the core technology. To make the connections survivable after various failure scenarios such as fiber cut and duct cut, it is necessary to consider SRLG diverse routing constraints in the traffic grooming problem. To jointly consider the working and backup paths, we first formulate the diverse routing problem into an Integer Linear Programming (ILP) process, in which the working and shared backup paths corresponding to a connection request are solved in a single step. We proposed failure-dependent SRLG protection heuristics algorithms for fiber selection. We compared the performance of various routing algorithms through simulation studies based on different metrics. Another contribution of this paper is a well-designed link-state metric is proposed for allocating the backup path and two selection schemes considering path costs are developed.
Our researches are based on such a system architecture that is intended to utilize the good characteristic of the interaction between millimeter-wave and lightwave to implement the 60GHz short millimeter-wave broadband wireless access system over fiber links. The networks include fiber optic links between the center stations (CS) and the base stations (BSs) and millimeter-wave air channel between the BSs and the networks terminals. The polymer optical fiber (POF) is deployed as optical fiber link medium due to its marked competitiveness in short haul, large capability communication systems. In this paper, we focus on suppressing dispersion of the radio-over-fiber transmission system. The POF is a dominant fiber chromatic dispersion source, which behaves multi-mode properties and produces inter-mode dispersion to heavily cause the POF bandwidth degradation. We present analysis on modal dispersion characteristics of 60 GHz short millimeter-wave broadband wireless access system over polymer optical fiber (POF) transmission link and present our scheme, which chooses proper launch condition to control the number of low-order modes and high-order modes excited in the POF link to improve system dispersion characteristic.
A share-controlled PFQ algorithm is proposed for IntServ EPON. It divides packet scheduling into high-priority phase and low-priority phase. In the high-priority phase, an improved PFQ algorithm is presented, which introduces a new constraint and a control factor into the scheduling discipline to overcome bandwidth preemption and to freely distribute excess bandwidth. Computer simulation results show that both the reserved services and non-reserved service can obtain excellent QoS performance when scheduled with the proposed algorithm.
We consider the problem of routing and wavelength assignment problem (RWA) in wavelength-routed networks, which consists of the Wavelength Division Multiplexers (WDM) and optical cross-connect (OXCs) devices interconnected via point-to-point WDM links. Assume that none of the OXCs has wavelength conversion capability. In this paper, we develop a set of dynamic distributed source-based DLE algorithms to provide primary and backup paths for connection requests with protection guarantee under single-link failures with local information. For better resource utilization, we employ multiplexing techniques, named primary backup multiplexing, to maximize the wavelength sharing among independent protection lightpaths. This technique allows a wavelength channel to be shared by a primary and one or more backup paths. We formulate the problem in link-based restoration context. The algorithm support on-demand path computation. Another main contribution is the introduction of the light-weight aggregated link metrics termed "barrel", we provide guidance to construct the protection routes with minimal wavelength consumption. We also compare the performance of various routing algorithms through simulation studies.
As a promising solution for the next generation broadband access network, Ethernet passive optical networks (EPONs) are being designed to deliver multiple services and applications, such as voice communications, video conferencing, real-time transactions and new evolving bandwidth-consuming applications. To support these applications with their various requirements, Quality-of-Service (QoS) management over EPON is required. In this study, we present a novel scheduling scheme, hierarchical weighted bandwidth guaranteed (HWBG) scheme, which could effectively support QoS. Simulation results validate that the proposed scheme can achieve high efficiency and improve packet delay performance.
Generalized Multiprotocol Label Switching (GMPLS), which is developed to support common control of packet, TDM, wavelength, and fiber services, is the key enabler of the new network model. The survivability of IP over WDM networks gains importance as network traffic keeps growing. In this paper, we propose an integrated provisioning scheme to dynamically allocate Label Switched Paths (LSPs) in IP over WDM networks. This scheme takes advantage of information sharing between layers (e.g., link state information, bandwidth usage, and protection capability) to eliminate redundancies and inefficiencies in the traditional layer-independent service provisioning. The integration of information is facilitated by GMPLS signaling. The proposed scheme also uses GMPLS capabilities to provide end-to-end survivability against network failures. The ability to provision across all network layers ensures efficient bandwidth usage. We propose two integrated routing algorithms: availability-based integrated routing algorithm and joint availability-based integrated routing algorithm. The simulation is made to evaluate the performance of our proposed integrated provisioning mechanism. As a result, network performance can be optimized over all layers. This could lead to significant cost savings for service providers.
To implement both fairness and priority scheduling in OLT scheduler, this paper proposes a SLA-supported packet fair queueing algorithm named R+WFQ. It employs WFQ discipline to serve high-priority sessions and Round Robin discipline to transmit low-priority sessions in free moments existed in traditional WFQ. Computer simulation results as well as theoretic analysis show that the proposed algorithm has excellent performance in terms of the implementation complexity, fairness and delay properties.
As a promising solution for next-generation broadband access networks, EPON could provide full-service access such as voice, video and data applications. However, EPON’s standard IEEE 802.3ah does not specify a particular supporting mechanism to guarantee QoS and priority requirements of various services, allowing it to be vendor specific. Meanwhile, how to segregate user traffic to guarantee security, remains unsolved. This paper creatively introduced the 802.1Q VLAN (Virtual Local Area Network) technique into the EPON system to solve these problems. Firstly, a brief introduction of EPON system is given. Secondly, the VLAN solution is presented in detail. Unlike VLAN mapping according to port or MAC in Gigabit Ethernet, EPON’s VLAN mapping is based on LLID tag. At last, OLT MAC layer design is given and FPGA implementation is described in detail. Detailed simulation experiments have been conducted to study the performance and validate the effectiveness of the proposed mechanism.
We consider the problem of routing and wavelength assignment problem (RWA) in wavelength-routed networks, which consists of the Wavelength Division Multiplexers (WDM) and optical cross-connect (OXCs) devices interconnected via point-to-point WDM links. Assume that none of the OXCs has wavelength conversion capability. The paper shows that the problem of RWA can be solved simultaneously by employing an efficient graph theoretic formulation, named as multi-layered graph model. On the basis of this notion, a heuristic RWA algorithm for static case is proposed. The numerical examples confirm that the proposed approach for static lightpath establishment (SLE) can obtain better solution for the number of requested lightpaths. The paper also considers the dynamic lightpath establishment (DLE) problem. We propose another heuristic DLE algorithm based on alternate-lightpath routing, according to a global selection criterion. We make a comparison of blocking probability according to different selection criterion. The performance of the proposed DLE algorithms is also evaluated and compared with that of the conventional algorithm via simulation of an arbitrary mesh network, where lightpath requests are assumed to arrive according to a Poisson process with exponentially distributed holding times.
KEYWORDS: Field programmable gate arrays, Multiplexers, Control systems, Computer programming, Optical networks, Fluorescence correlation spectroscopy, Error control coding, Passive optical networks, Operating systems, Fiber to the x
Ethernet passive optical network (EPON), which represents the convergence of low-cost, high-bandwidth and supporting multiple services, appears to be one of the best candidates for the next-generation access network. The work of standardizing EPON as a solution for access network is still underway in the IEEE802.3ah Ethernet in the first mile (EFM) task force. The final release is expected in 2004. Up to now, there has been no standard application specific integrated circuit (ASIC) chip available which fulfills the functions of media access control (MAC) layer of EPON. The MAC layer in EPON system has many functions, such as point-to-point emulation (P2PE), Ethernet MAC functionality, multi-point control protocol (MPCP), network operation, administration and maintenance (OAM) and link security. To implement those functions mentioned above, an embedded real-time operating system (RTOS) and a flexible programmable logic device (PLD) with an embedded processor are used. The software and hardware functions in MAC layer are realized through programming embedded microprocessor and field programmable gate array(FPGA). Finally, some experimental results are given in this paper. The method stated here can provide a valuable reference for developing EPON MAC layer ASIC.
In implementing EPON systems, one of key challenges is designing bandwidth scheduling scheme to achieve network efficiency and meet various QoS requirements. This paper proposes a novel scheduling algorithm over EPON based on sliding window mechanism, which divides a transmission circle into two sections and introduces bandwidth sliding window substituting for the conception of fixed maximum window. Computer simulation results show that the performance of the proposed algorithm is effectively improved in terms of packet delay and upstream channel utilization.
EPON (Ethernet Passive Optical Network) is a new technology for access network based on Ethernet protocol. In this paper, a system model is established to simulate the EPON system. The different noise sources that affect the system performance are taken into account, including 1ST, MIPN, RIN, Extinction Ratio, etc. Not only the system performance degradation induced by burst-mode reception but also the requirement and effect of FEC are considered. The optimal system parameters are found to achieve a tradeoff between system performance and cost. At last, a technical scheme technically and economically feasible for China is put forward. More attention is paid to the burst mode operation which leads to the system performance degradation. A theoretical model is adopted to determine the sensitivity penalty caused by burst mode reception.
Synchronization is one of the difficult problems in realization of Ethernet PON receiver, because the bit rate is as high as 1 .25Gb/s and the receivers works in burst mode. Burst mode synchronization relates to two key techniques: ranging and phase adjustment. For these two key techniques, this paper puts forward a ranging flow for the Ethernet PON system and a novel burst mode synchronization circuit running at 1.25Gbps. Using VHDL, the algorithm and the structure of ranging could be realized, and the result of simulation is provided. The performance of the ranging flow is compared for the different collision resolution algorithm. At the same time, the feasibility and the performance of a high speed burst synchronization circuit are presented with the simulation result.
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