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Lightwave Technology, Journal of

Issue 21 • Date Nov.1, 2011

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  • [Front cover]

    Publication Year: 2011 , Page(s): C1
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  • Journal of Lightwave Technology publication information

    Publication Year: 2011 , Page(s): C2
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  • Table of contents

    Publication Year: 2011 , Page(s): 3117 - 3118
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  • Statistics of Group Delays in Multimode Fiber With Strong Mode Coupling

    Publication Year: 2011 , Page(s): 3119 - 3128
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1682 KB) |  | HTML iconHTML  

    The modal group delays (GDs) are a key property governing the dispersion of signals propagating in a multimode fiber (MMF). An MMF is in the strong-coupling regime when the total length of the MMF is much greater than the correlation length over which local principal modes can be considered constant. In this regime, the GDs can be described as the eigenvalues of zero-trace Gaussian unitary ensemble, and the probability density function (pdf) of the GDs is the eigenvalue distribution of the ensemble. For fibers with two to seven modes, the marginal pdf of the GDs is derived analytically. For fibers with a large number of modes, this pdf is shown to approach a semicircle distribution. In the strong-coupling regime, the delay spread is proportional to the square root of the number of independent sections, or the square root of the overall fiber length. View full abstract»

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  • Impact of the Scalar Approximation on the Prediction of the Group Velocity Dispersion

    Publication Year: 2011 , Page(s): 3129 - 3134
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (825 KB) |  | HTML iconHTML  

    A detailed study of the impact of using a scalar approximation to the wave equation on the prediction of the group velocity dispersion is shown by comparing predictions against results obtained by using a full-vectorial wave equation and measurements of commercially available optical fibers. The effect is significant for fibers with large waveguide dispersion, such as highly nonlinear and dispersion compensating fibers. View full abstract»

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  • Cost-Effective Introduction and Energy-Efficient Operation of Long-Reach WDM/TDM PON Systems

    Publication Year: 2011 , Page(s): 3135 - 3143
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1277 KB) |  | HTML iconHTML  

    Cost effectiveness and energy efficiency have recently become two practical issues during access networks construction and operation. In this paper, we extend our previous proposal of a remote channel combine/split module for long-reach wavelength division multiplexed and time division multiplexed passive optical network systems. Besides previously discussed benefits on investment cost and energy efficiency under take-up-rate-adaptive mode, this study shows that proposed systems help achieve higher energy saving by adopting traffic-adaptive power management. Simulation results show up to 35% power consumption saving at the time of minimum traffic demands. Moreover, in terms of energy consumption over periodic time, we find a typical 20% energy saving can be achieved compared to conventional systems in fully operated stage. View full abstract»

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  • Generalized Tensor Analysis Model for Multi-Subcarrier Analog Optical Systems

    Publication Year: 2011 , Page(s): 3144 - 3155
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (874 KB) |  | HTML iconHTML  

    We propose and develop a general tensor analysis framework for a subcarrier multiplex analog optical fiber link for applications in microwave photonics. The goal of this work is to construct an uniform method to address nonlinear distortions of a discrete frequency transmission system. We employ tensorial representation, i.e., multidimensional arrays, to unify the multi-subcarrier intermodulation effect. Based on the tensorial expression of the optical field in a subcarrier vector space, various kinds of modulation methods, dispersive transmission as well as detection schemes are specified. In addition, it is demonstrated that each corresponding tensor is formally determined by device structures, which allows for a synthesized study of device combinations more systematically. For implementing numerical methods, the practical significance of the tensor model is it simplifies the derivation details compared with series-based approaches by hiding the underlying multi-fold summation and index operation. The integrity of the proposed methodology is validated by investigating the classical intensity modulated system. Furthermore, to give an application model of the tensor formalism, we make a study of two multi-subcarrier systems with detailed performance discussions. We believe the tensor model provides us not only a consolidated notation, but also an alternative numerical approach to effectively analyze multi-subcarrier analog optical systems. View full abstract»

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  • Loss-Relevant Structural Imperfections in Substrate-Type Photonic Crystal Waveguides

    Publication Year: 2011 , Page(s): 3156 - 3166
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1362 KB) |  | HTML iconHTML  

    Substrate-type planar 2-D photonic crystal (PhC) waveguides suffer from large experimental propagation losses compared to membrane-type PhC waveguides. Numerical simulations can give insight into the quantitative contribution to the propagation losses originating from fabrication imperfections and nonideal designs of the waveguide or the vertical layer structure. Many numerical studies have been performed in the past addressing only a part of the question. All of them lack the general overview, which is essential to identify the main source for the large propagation losses. Since those studies are performed with various numerical methods on many different PhC waveguide designs, a general overview cannot be reliably assembled from the literature. Therefore, we (re-)performed a comprehensive set of numerical experiments with the 3-D finite-difference time-domain method to investigate the influences of imperfections, such as the finite etch depth, a conical hole shape, the finite number of lateral layers of holes, the asymmetric vertical layer structure, lattice disorder, and variations of the hole radius. A major result of this paper is a list of requirements to be met by the process technology for the fabrication of a W1 PhC waveguide in the low-index contrast system (InP/InGaAsP/InP). Furthermore, we were able to identify the angled sidewalls to be responsible for the main fabrication-related propagation loss contribution. Finally, we show the potential of new, alternative low-loss waveguide designs for the weak index contrast system and emphasize the importance of using realistic hole shapes in this search process. View full abstract»

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  • Influence of Transmission Impairments on the OSMOSIS HPC Optical Interconnect Architecture

    Publication Year: 2011 , Page(s): 3167 - 3177
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1132 KB) |  | HTML iconHTML  

    We examine the impact of transmission impairments on the performance of the optical supercomputer interconnect architecture, initially proposed in the context of the optical shared memory supercomputer interconnect system (OSMOSIS) project. We study two versions of the aforementioned optical interconnect that differ in terms of the number of semiconductor optical amplifiers (SOAs) used as ON-OFF gates. For practical reasons related to packet arbitration, the size of the crossbar switch of the optical interconnect in this study is limited to 64 ports. The switch is based on a broadcast-and-select architecture and employs DWDM in conjunction with 10 Gb/s intensity modulation/direct detection per wavelength channel. We show, both by experiment and by simulation, that the minimization of the number of SOAs in the optical switch by taking advantage of the cyclic routing capability of optical arrayed waveguide multiplexers/demultiplexers leads to negligible performance deterioration compared to conventional wavelength-space switches that are prohibitive slower and do not use any inherent gain properties like in OSMOSIS. View full abstract»

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  • Distributed Polarization-Sensitive Reflectometry in Nonreciprocal Single-Mode Optical Fibers

    Publication Year: 2011 , Page(s): 3178 - 3184
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (431 KB) |  | HTML iconHTML  

    We present a novel theoretical model for the description of round-trip propagation of polarized optical signals in single-mode fibers affected by nonreciprocal birefringence. The model has a general validity, but it has been specialized to the case of Faraday rotation. Building on the theoretical result, we propose also a method to measure both reciprocal and nonreciprocal birefringence of single-mode fibers by means of polarization-sensitive reflectometry. The theoretical model and the measurement technique have been tested in a preliminary experiment, which consisted in measuring the static magnetic field of a 1.5 T magnetic resonance imaging scanner. Experimental results are in agreement with the theory. View full abstract»

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  • A 320 Gb/s-Throughput Capable 2 ,\times, 2 Silicon-Plasmonic Router Architecture for Optical Interconnects

    Publication Year: 2011 , Page(s): 3185 - 3195
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1084 KB) |  | HTML iconHTML  

    We demonstrate a 2 × 2 silicon-plasmonic router architecture with 320 Gb/s throughput capabilities for optical interconnect applications. The proposed router platform relies on a novel dual-ring Dielectric-Loaded Surface Plasmon Polariton (DLSPP) 2 × 2 switch heterointegrated on a Silicon-on-Insulator (SOI) photonic motherboard that is responsible for traffic multiplexing and header processing functionalities. We present experimental results of a Poly-methyl-methacrylate (PMMA)-loaded dual-resonator DLSPP waveguide structure that uses two racetrack resonators of 5.5 μm radius and 4 μ m-long straight sections and operates as a passive add/drop filtering element. We derive its frequency-domain transfer function, confirm its add/drop experimental spectral response, and proceed to a circuit-level model for dual-ring DLSPP designs supporting 2 × 2 thermo-optic switch operation. The validity of our circuit-level modeled 2 × 2 thermo-optic switch is verified by means of respective full vectorial three-dimensional Finite Element Method (3D-FEM) simulations. The router setup is completed by means of two 4 × 1 SOI multiplexing circuits, each one employing four cascaded second order micro-ring configurations with 100 GHz spaced resonances. Successful interconnection between the DLSPP switching matrix and the SOI circuitry is performed through a butt-coupling design that, as shown via 3D-FEM analysis, allows for small coupling losses of as low as 2.6 dB. The final router architecture is evaluated through a co-operative simulation environment, demonstrating successful 2 × 2 routing for two incoming 4-wavelength Non-Return-to-Zero (NRZ) optical packet streams with 40 Gb/s line-rates. View full abstract»

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  • Survivable Hierarchical Optical Path Network Design With Dedicated Wavelength Path Protection

    Publication Year: 2011 , Page(s): 3196 - 3209
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1139 KB) |  | HTML iconHTML  

    In this paper, we propose a novel network design algorithm that yields the hierarchical optical path network with dedicated wavelength path protection. A hierarchical optical path network provides two granularities in implementing dedicated protection in the optical layer, namely waveband path protection and wavelength path protection. The characteristics of both protection mechanisms are investigated. We develop the concept of the source-destination Cartesian product space to aggregate closely located traffic demands, which leads to a significant reduction in network resources needed. The proposed wavelength path protection algorithm achieves lower network costs than that possible with waveband protection when traffic volume is relatively small. On the other hand, in the large traffic demand area, both schemes offer almost the same cost, which makes the waveband protection scheme attractive because of its operational simplicity. Numerical results clarify that survivable hierarchical optical path network is more cost effective than the single layer optical path network with optical layer protection, irrespective of which protection scheme is utilized. View full abstract»

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  • Security in Photonic Networks: Threats and Security Enhancement

    Publication Year: 2011 , Page(s): 3210 - 3222
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1507 KB) |  | HTML iconHTML  

    We address emerging threats to the security of photonic networks as these networks become heterogeneous being opened to the upper layers, other operators, and end users. We review the potential threats, mainly loss of the confidentiality of user data transmitted through optical fibers and disturbances of network control, both of which could seriously damage the entire network. We then propose a novel conceptual model of a secure photonic network by introducing a quantum key distribution (QKD) network to its legacy structure. Secure keys generated by the QKD network are managed by key management agents (KMAs) and used to encrypt not only user data but also control signals. The KMAs cooperate with the generalized multiprotocol label-switching controller for secure path provisioning and drive photonic and modern crypto engines in appropriate combinations. Finally, we present a roadmap of a deployment scenario, starting from niche applications such as mission critical and business applications and the next. Digital cinema distribution through a photonic network is presented as an example of a niche application. View full abstract»

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  • Impact of Channel Count and PMD on Polarization-Multiplexed QPSK Transmission

    Publication Year: 2011 , Page(s): 3223 - 3229
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1658 KB) |  | HTML iconHTML  

    Through graphics-processing-unit-based simulations with different numbers of copropagating channels (1--81), the dependence of the nonlinear threshold on channel count, as well as on the fiber polarization mode dispersion (PMD) coefficient, is investigated for both dispersion-managed and DCM-free 40 and 100 Gb/s coherent-detected polarization-multiplexed quadrature phase-shift keying (CP-QPSK) transmission systems. Different fiber types including standard single-mode fiber (SSMF), large effective area fiber (LEAF), and truewave classic fiber (TWC) are considered and compared. Our investigations show that the required number of simulated copropagating channels to correctly simulate the nonlinear penalty caused by interchannel nonlinearities on CP-QSPK modulation is strongly dependent on the fiber type. The generally used assumption of around ten channels for simulating interchannel nonlinearities is only valid for the SSMF with relative low channel input power. For transmission links consisting of fiber types with low dispersion or high nonlinear coefficients, such as the LEAF or TWC, ten copropagating channels are clearly not sufficient. In dispersion-managed systems with DCMs, the required number of simulated copropagating channels is not only dependent on fiber types and data rates but also strongly on PMD present in the links. Our investigations have indicated that for transmission over fibers with very low PMD (this is the case of most new fibers), ten copropagating channels are not sufficient to correctly characterize the interchannel nonlinearities even for high-dispersion fiber types, such as the SSMF, and hence causes a clear underestimation of the nonlinearity penalty. Finally, synchronized and interleaved CP-QPSK is compared. We show that despite the depolarization effect of PMD, there are still some benefits of using interleaved RZ-CP-QPSK systems. View full abstract»

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  • Dispersion Relation of Leaky Modes in Nonhomogeneous Waveguides and Its Applications

    Publication Year: 2011 , Page(s): 3230 - 3236
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1519 KB) |  | HTML iconHTML  

    For a nonhomogeneous waveguide, whose refractive index is not a constant, the problem is very complicated since the nonlinear eigenvalue problems are unable to reduce to algebraic equations yet. When the refractive index is varied, the dispersion relation cannot be derived by using the analytic expressions of the solutions in each layer. In this paper, this problem is solved by using the differential transfer matrix method, which is introduced to deduce the dispersion relations of leaky modes for TE and TM cases, respectively. Moreover, for the waveguide whose refractive index is gradually varied, the dispersion relations can be approximated by some simpler algebraic equations, which are close to the exact relations and very easy to analyze. Asymptotic solutions are used as initial guesses, and followed by Newton's method, to give very accurate solutions. This paper is a generalization of the asymptotic method of slab waveguides; all the results therein are consistent with the analysis here. View full abstract»

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  • Hybrid Mode Locked Fiber Laser Using a PDMS/SWCNT Composite Operating at 4 GHz

    Publication Year: 2011 , Page(s): 3237 - 3242
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (221 KB) |  | HTML iconHTML  

    A hybrid mode-locked Erbium-doped fiber laser that provides very short pulse-widths while achieving high repetition rates is proposed and experimentally demonstrated. This hybrid configuration is realized by using a thin film of polydimethylsiloxane (PDMS) doped with single wall carbon nanotubes (SWCNT). This PDMS/SWCNT composite acts as a saturable absorber and is inserted within an active mode-locked laser system using angled connectors. Therefore, the effect of the PDMS/SWCNT composite is to effectively narrow the width of the pulses generated by the active system without modifying its repetition rate. A pulse-width of 730 fs was generated at a repetition rate of 4 GHz, while achieving an average output power of 4 mW. A reduction in the noise of the photodetected RF spectrum was also observed in the hybrid system. View full abstract»

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  • Modeling and Analysis of Microring Resonator Modulators With Feedback Waveguide Coupling

    Publication Year: 2011 , Page(s): 3243 - 3249
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB) |  | HTML iconHTML  

    The model and dynamic numerical solution of microring resonator modulators with feedback waveguide coupling are proposed and used to analyze the modulation performance. The sinusoidal intensity modulation output and bandwidth are presented. The feedback arm modulation manner is potential to ensure stable output with frequency increasing and wide bandwidth. Phase characteristics studies show that the resonator is suitable for phase shift keying. Furthermore, the Gaussian pulse modulation is studied. Results show that linear and undistorted output can be achieved for narrow and high speed pulse modulation while the resonator is biased at critical coupling position. View full abstract»

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  • Flow Scheduling in Optical Flow Switched (OFS) Networks Under Transient Conditions

    Publication Year: 2011 , Page(s): 3250 - 3264
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1030 KB) |  | HTML iconHTML  

    Optical flow switching (OFS) has been recently introduced as a potential “green” architecture addressing the power issue of store-and-forward packet switching in future MAN-WAN Terabit networks. One key architectural component of OFS differentiating it from other “green” WAN architectures such as optical circuit switching (OCS), optical packet switching (OPS) and optical burst switching (OBS), is its centralized flow scheduling. Comparing the theoretical network capacity regions of OFS, OCS, OPS and OBS has revealed that the dominating theoretical capacity depends on the hardware as well as on the port configuration. The dominating actual capacity (throughput) that can be achieved also depends on the flow schedulers supported by each architecture. Since centralized scheduling incorporated in OFS is the least restricting between all scheduling methods, OFS is a promising “green” architecture option for future MAN-WAN Terabit networks. For better understanding the actual potential throughput of OFS, we study its scheduling problem in a realistic traffic model where lightpath requests arrive as a time-dependent Poisson process with Pareto distributed lightpath service times. Lightpath schedules are taken at fixed time intervals (larger than 100 ms) in a central node and flows that have already been scheduled cannot be interrupted before their completion. The scheduling problem is represented as a discrete-time Markov decision process where the objective function is given by the flow blocking probability over a finite time horizon. We derive three lower bounds to the objective function and propose several schedulers, with and without fairness requirements. The performance of our OFS schedulers are evaluated under both static and limited dynamic routing, by emulating the algorithms on random network topologies for two hours. The main result is that our proposed max-min fair scheduler with limited dynamic routing significant- - ly outperforms all other schedulers with static routing. Furthermore, its blocking probability is close to the lower bound for static routing. View full abstract»

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  • Dimensioning the Add/Drop Contention Factor of Directionless ROADMs

    Publication Year: 2011 , Page(s): 3265 - 3274
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (823 KB) |  | HTML iconHTML  

    Reconfigurable Optical Add/Drop Multiplexers (ROADM) are the optical switching equipment of transparent optical networks. Directionless ROADMs permit the network carriers to change the direction of an added and/or dropped lightpath without the need of a technician on-site intervention in the lightpath end nodes. Colorless ROADMs provide the same versatility for changing the lightpath transmission wavelength. Cost-effective directionless ROADM architectures (colorless or colored) can be built if the maximum number of lightpaths that can be added/dropped using the same wavelength is limited. We name this limit as the node add/drop contention factor, and denote it as C. In this paper we investigate the network lightpath blocking performance as a function of this add/drop contention factor of the nodes. The scenarios considered are the static planning of a network (i) with unprotected traffic, (ii) with traffic 1+1 protected for single-link failures, and (iii) with traffic 1+1 protected for single-link or single-node failures. Since for these scenarios, the wavelength of an existing lightpath does not have to be dynamically reconfigured, the work in this paper applies to both colorless and colored nodes. An ILP model and an effective heuristic are presented to solve the so-called Add/Drop Contention Aware RWA (ADCA-RWA) planning of the network. Extensive results are reported. In all the cases, an add/drop factor C = 2 is sufficient to provide the same performance as contentionless nodes (C = ∞). Furthermore, in all the tests a factor C = 1 was also sufficient, or produced a minor lightpath blocking performance degradation (below 0.5% in the unprotected cases, and below 2.5% in the 1 + 1 protected cases). View full abstract»

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  • Nonlinear Effects Mitigation in Coherent Optical OFDM System in Presence of High Peak Power

    Publication Year: 2011 , Page(s): 3275 - 3281
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1626 KB) |  | HTML iconHTML  

    The nonlinear effects of Mach-Zehnder modulator (MZM) and self phase modulation (SPM), in optical orthogonal frequency division multiplexing (OFDM) under the presence of high peak power is studied. A full coherent optical communication system is presented and analyzed. Standard method to reduce the peak to average power ratio (PAPR) values combined with improved technique to mitigate the nonlinear effect, by means of optimized digital pre-distortion, is analyzed and a full performance analysis is presented. View full abstract»

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  • Performance Evaluation of Digital Coherent Receivers for Phase-Modulated Radio-Over-Fiber Links

    Publication Year: 2011 , Page(s): 3282 - 3292
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1904 KB) |  | HTML iconHTML  

    The performance of optical phase-modulated (PM) radio-over-fiber (RoF) links assisted with coherent detection and digital signal processing (PM-Coh) is analyzed and experimentally demonstrated for next-generation wireless-over-fiber systems. PM-Coh offers high linearity for transparent transport of high-frequency microwave signals, and better receiver sensitivity than intensity modulated with direct detection systems. By including photonic downconversion in the PM-Coh link, in a form of a pulsed free-running local oscillator, it is possible to receive high-RF carrier frequencies, with low-bandwidth electronics. Analytical assessment and simulations are used to determine the ultimate performance with respect to laser linewidth, modulation index, and receiver sensitivity. Then, two different scenarios are studied and experimentally demonstrated as an application of PM-Coh links: a high-capacity multiantenna RoF system (12 subcarriers of 400 Mb/s and 6 subcarriers of 800 Mb/s) and photonic downconversion for the detection of high-RF carriers microwave signals (up to 3.2 Gb/s at 40 GHz). View full abstract»

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  • Study of Power Control on Double-Weight Codes With an Arbitrary Maximum Cross-Correlation Value in Variable-QoS Optical CDMA

    Publication Year: 2011 , Page(s): 3293 - 3303
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB) |  | HTML iconHTML  

    In this paper, the use of power and weight control in multimedia, variable quality-of-services (QoS) incoherent optical code-division multiple-access (O-CDMA) systems in on-off keying is studied. An adjustable-power and variable-weight incoherent O-CDMA architecture is presented and the general performance model of 1-D and 2-D double-weight optical codes with an arbitrary maximum cross-correlation value λc is formulated as functions of code weight and chip power. Our results show that the performance of double-weight codes can be fine-tuned by varying both code weight and power, and they play different roles in the QoS differentiation. From the numerical examples, we show that λc=2 double-weight codes can perform as good as their λc=1 counterparts and, at the same time, have the advantage of supporting more possible subscribers. This general analytical model is important for power-sensitive applications, such as in-service monitoring and fiber-fault surveillance in optical networks and sensor-identification in fiber-sensor systems with the use of optical codes. View full abstract»

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  • High-Resolution Tunable RF/Microwave Photonic Notch Filter With Low-Noise Performance

    Publication Year: 2011 , Page(s): 3304 - 3309
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (211 KB) |  | HTML iconHTML  

    A new high-resolution tunable RF/microwave photonic notch filter with low-noise performance is presented. It is based on using a dual-input electro-optic intensity modulator together with a frequency-shifting amplified recirculating delay line loop. It can realize a very narrow notch, and also a wide and flat passband to simultaneously excise interference with minimal impact on the wanted signal. The notch filter can be integrated into optical fibre microwave transmission systems. Experimental results are presented which demonstrate a notch filter response with a very narrow notch width of 0.55% of the filter free spectral range, a wide and flat passband, and a high signal-to-noise ratio of 114 dB/Hz. The ability to tune the notch frequency of the filter is also demonstrated. View full abstract»

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  • Achieving Higher Modulation Efficiency in Electrooptic Polymer Modulator With Slotted Silicon Waveguide

    Publication Year: 2011 , Page(s): 3310 - 3318
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1696 KB) |  | HTML iconHTML  

    Silicon slot waveguide based Mach-Zehnder interferometric modulators with electrooptic polymers in the slot have the advantage of low half-wave voltage-length product (Vπ *L). Several key aspects of this unconventional electrooptic polymer modulator design to optimize the modulator performance are studied in this work. Both computer simulation and experiments have been conducted to understand the relationship between modulator performance such as modulation efficiency, optical loss and the waveguide design parameters. Techniques to achieve efficient poling of electrooptic polymers in the silicon slot waveguide have been developed. The doping of the silicon to enhance conductivity for efficient poling and the trade-off between conductivity and optical loss are experimentally investigated. Surface passivation of silicon nanophotonic structures has been found to be effective in improving poling efficiency. By applying these techniques to a silicon slot waveguide Mach-Zehnder modulator, a low Vπ*L of 0.52 V ·cm has been achieved. Finally travelling wave electrode designs have been evaluated and the results show that the bandwidth is mainly limited by the attenuation of the radio frequency signal in the electrode and a standard coplanar waveguide electrode design is able to reach 20 GHz in modulators of silicon slot waveguide embedded in electrooptic polymer. View full abstract»

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  • Individually Switchable and Widely Tunable Multiwavelength Erbium-Doped Fiber Laser Based on Cascaded Mismatching Long-Period Fiber Gratings

    Publication Year: 2011 , Page(s): 3319 - 3326
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (993 KB) |  | HTML iconHTML  

    A novel concept of individually switchable and widely tunable erbium-doped multiwavelength fiber laser (MWFL) is proposed and experimentally demonstrated. The key component of the laser is a channel transmissivity individually variable comb filter composed of two cascaded different-length long-period fiber gratings (LPFGs), named cascaded mismatching LPFGs. When inserted into the laser cavity, this polarization-dependent comb filter functions as the wavelength selector and switching filter simultaneously. By properly adjusting the polarization controllers (PCs) in the laser cavity and in the high birefringence Sagnac loop mirror (HiBi-SLM), eleven individually switchable wavelengths with different flexible lasing states, including successively tunable adjacent single-, dual- and triple-wavelength outputs, nonadjacent dual- and triple-wavelength outputs, as well as quadruple- and quintuple-wavelength outputs, have been achieved. This MWFL may be useful in optical fiber sensing or other fields desiring very flexible optical source. View full abstract»

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Aims & Scope

The Journal of Lightwave Technology contains articles on current research, applications and methods used in lightwave technology and fiber optics.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Peter J. Winzer
Alcatel-Lucent Bell Labs