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Lightwave Technology, Journal of

Issue 17 • Date Sept.1, 2012

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Displaying Results 1 - 25 of 34
  • Front Cover

    Publication Year: 2012 , Page(s): C1
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    Freely Available from IEEE
  • Journal of Lightwave Technology publication information

    Publication Year: 2012 , Page(s): C2
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  • Table of Contents

    Publication Year: 2012 , Page(s): 2749 - 2750
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  • A Large Serial Time-Division Multiplexed Fiber Bragg Grating Sensor Network

    Publication Year: 2012 , Page(s): 2751 - 2756
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (800 KB) |  | HTML iconHTML  

    We demonstrated a wavelength scanning time division multiplexing of 1000 ultra-weak fiber Bragg gratings (FBG) for distributed temperature sensing. The strong multiplexing capability and low crosstalk of the ultra-weak FBG sensors is investigated through both theoretical analysis and experiment. An automated FBG fabrication system was developed for fast 1000-FBG fabrication. The measurement accuracy of Bragg wavelengths for more than 80% FBGs is less than 20 pm, corresponding to 2 ^{\circ} C in temperature. View full abstract»

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  • DFT-Precoded Coherent Optical OFDM With Hermitian Symmetry for Fiber Nonlinearity Mitigation

    Publication Year: 2012 , Page(s): 2757 - 2763
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1261 KB) |  | HTML iconHTML  

    Coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems have inferior nonlinear performance due to their high peak to average power ratio (PAPR) characteristics. In order to mitigate fiber nonlinearities for the CO-OFDM systems, we propose a novel discrete Fourier transform (DFT)-precoded coherent optical OFDM combined with a Hermitian symmetry (DFT-precoded HS CO-OFDM) system, which is a combination of the DFT-spread OFDM and the Hermitian symmetry of the DFT. Furthermore, the proposed system can be easily implemented by using a fast Fourier transform (FFT) algorithm. Because the proposed system has a lower PAPR than the conventional CO-OFDM system, the DFT-precoded HS CO-OFDM system provides superior nonlinear tolerance. Moreover, the proposed system is superior to the conventional DFT-spread coherent optical OFDM (DFT-spread CO-OFDM) system in terms of maintaining low PAPR in optical fiber transmission. The low PAPR in the proposed scheme is suitable for long-haul optical transmission systems, compared with the conventional DFT-spread CO-OFDM. For the DFT-precoded HS OFDM system, we have developed a theoretical framework illustrating the principles of the proposed system. The numerical results show that the DFT-precoded HS CO-OFDM system outperforms the conventional CO-OFDM by 5.4% EVM performance after 1200-km transmission and the conventional DFT-spread CO-OFDM by 4.5% EVM performance after 2800-km transmission at a fiber launch power of {-}2 dBm. View full abstract»

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  • Spatio-Temporal Self-Focusing in Femtosecond Pulse Transmission Through Multimode Optical Fibers

    Publication Year: 2012 , Page(s): 2764 - 2769
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (571 KB) |  | HTML iconHTML  

    We numerically investigate ultra-short pulse propagation in multimode optical fibers with launch peak powers approaching the critical power for self-focusing using a generalized multimode nonlinear Schrödinger equation approach. Nonlinear spatial and temporal effects combined with fiber dispersion govern pulse compression in space and time which can result in damage-inducing intensity levels. Here we identify pulse parameters for which damage is avoided and high-power delivery through optical fiber is possible near the fiber zero-dispersion wavelength. View full abstract»

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  • Er-Doped Fiber Laser Mode-Locked by CVD-Graphene Saturable Absorber

    Publication Year: 2012 , Page(s): 2770 - 2775
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (952 KB) |  | HTML iconHTML  

    Erbium-doped fiber laser passively mode-locked by bilayer graphene is presented. The graphene layers were grown by chemical vapor deposition (CVD) on Cu substrate and transferred onto a fused silica window, forming a saturable absorber (SA). Low non-saturable losses and modulation depth as high as 55% allowed to achieve soliton pulses with over 11 nm bandwidth and nearly-transform limited 315 fs duration at 1564 nm center wavelength. The paper describes the design of the laser construction, as well as the graphene-SA preparation process. Our study demonstrates, that CVD-Cu graphene transferred on glass substrate may be used for efficient mode-locking of fiber lasers. View full abstract»

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  • Cross-Sectional Shape Optimization of Whispering-Gallery Ring Resonators

    Publication Year: 2012 , Page(s): 2776 - 2782
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (919 KB) |  | HTML iconHTML  

    Optimal cross-sectional shapes of whispering-gallery ring resonators with prescribed emission wavelength and resonance mode are generated using topology optimization based on the finite element method. The two critical performance indices, the quality factor (Q factor) and mode volume of a resonator, are treated as the objective functions in the optimization. In our numerical study, characteristics of optimal configurations are identified and analyzed. Since the Q factor and mode volume have a tradeoff relationship, i.e., an increasing Q factor increases mode volume, a Pareto-optimal set of solutions can be identified under certain device specifications. These configurations achieve better performances than existing shapes in producing both a high Q factor and low mode volume. View full abstract»

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  • Differential Mode Delay Managed Transmission Line for WDM-MIMO System Using Multi-Step Index Fiber

    Publication Year: 2012 , Page(s): 2783 - 2787
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB) |  | HTML iconHTML  

    We proposed a mode group delay managed transmission line for a WDM-MIMO system consisting of fibers with positive and negative DMDs to compensate for the total DMD. We show numerically that the multi-step index fiber can flexibly tune the DMD. We fabricated fibers for use in a C-L band WDM-MIMO system, and realized a 20.4 km-long DMD compensated transmission line with a total absolute DMD of less than 111 ps over the entire C-L band. Finally, we achieved a 2 ,\times, 2 WDM-MIMO transmission within the C-L band by using equalizers with a small tap number. View full abstract»

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  • On Exploiting Sharable Resources With Resource Contention Resolution for Surviving Double-Link Failures in Optical Mesh Networks

    Publication Year: 2012 , Page(s): 2788 - 2795
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1842 KB) |  | HTML iconHTML  

    As the size and the complexity of optical mesh networks grow, double-link failures become more probable. To protect against double-link failures, we generally have to provision more backup resources with respect to single-link failures. To improve the resource efficiency, it is important to reduce backup resources used for surviving double-link failures. In this paper, we investigate some representative sharing schemes and propose an enhanced resource sharing scheme with resource contention resolution for double-link failures in survivable optical mesh networks. By fully taking into account the temporal and spatial factors, our scheme can accommodate reasonable contention for sharing resources and minimize backup resources for reservation with 100% protection guarantee. Simulation results show that this enhanced resource sharing scheme can achieve satisfactory performance in terms of resource utilization ratio and blocking probability. View full abstract»

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  • Analysis and Implementation of Reflection-Type Electro-Optic Phase Diffraction Grating

    Publication Year: 2012 , Page(s): 2796 - 2802
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    A reflection-type electro-optic phase diffraction grating using the novel transparent lead magnesium niobate-lead titanite (PMNT) electro-optic ceramic is analyzed theoretically and implemented experimentally. The Au/Ti interdigital electrodes are sputtered on one surface of ceramic wafer which is used to change the material refractive index by the quadratic electro-optic effect. The phase modulation characteristic and the optical beam diffraction patterns induced by a controllable electric field are analyzed theoretically and simulated numerically. Using a high electro-optic coefficient transparent PMNT ceramic wafer, some experimental results are given to verify the theoretical analysis and they are accordant very well. Finally, some potential applications for the reflection-type electro-optic phase diffraction grating in the ultrafast laser application areas are also discussed in this paper. View full abstract»

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  • Pulse Propagation in a Short Nonlinear Graded-Index Multimode Optical Fiber

    Publication Year: 2012 , Page(s): 2803 - 2811
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1554 KB) |  | HTML iconHTML  

    We present a detailed analysis of the modal properties, dispersive behavior, and nonlinear mode coupling in graded-index multimode fibers (GIMFs), and lay out a simplified form of a generalized nonlinear Schrödinger equation, which can be used to explore the rich nonlinear dynamics related to the propagation and interaction of light pulses in GIMFs in a tractable manner. We also briefly discuss an application of the presented formalism in the study of four-wave mixing in these fibers. While the reported formalism is fairly general, our presentation is mainly targeted at device applications in which short segments of GIMFs are used. View full abstract»

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  • Wideband Slow Light With Large Group Index and Low Dispersion in Slotted Photonic Crystal Waveguide

    Publication Year: 2012 , Page(s): 2812 - 2817
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (862 KB) |  | HTML iconHTML  

    Slow light in slotted photonic crystal waveguide is a promising approach for practical applications. Two of the crucial concerns of this technology are the limited bandwidth and the pulse broadening. It was demonstrated that wideband slow light with large group index and low dispersion could be realized by shifting the first and second rows of air holes adjacent to the slot. Keeping the group index at 28, 41, and 105, respectively, the corresponding bandwidths of flat and low dispersion band could reach 17, 6.8, and 1.7 nm around 1550 nm. To further enlarge the bandwidth and group index, the oblique structure was introduced, and the bandwidths over 23.6, 6, and 1.8 nm were achieved with the group index of 30, 45, and 110, respectively. Then the propagation of slow light optical pulse was performed in time domain by the finite-difference time-domain method and a resonant structure was designed for input and output interfaces to improve the coupling efficiency. View full abstract»

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  • Efficient, Wide Angle, Structure Tuned 1 ,\times, 3 Photonic Crystal Power Splitter at 1550 nm for Triple Play Applications

    Publication Year: 2012 , Page(s): 2818 - 2823
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (962 KB) |  | HTML iconHTML  

    We propose a wide angle, efficient and low loss 1 ?? 3 power splitter based on triangular lattice air holes silicon slab Photonic Crystal (PhC). Desired power splitting ratio was achieved by altering the structure at the junction area of the power splitter. Simulation results obtained using 2-D finite difference time domain method show that for TE polarization incident signal, the power is distributed almost equally with total normalized transmission of 99.74% and negligible reflection loss at the 1550 nm optical operating wavelength. In addition, the power splitter can operate at 1388 nm and 1470 nm optical wavelengths. View full abstract»

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  • Convergence of 60 GHz Radio Over Fiber and WDM-PON Using Parallel Phase Modulation With a Single Mach–Zehnder Modulator

    Publication Year: 2012 , Page(s): 2824 - 2831
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1687 KB) |  | HTML iconHTML  

    We propose a converged radio over fiber and wavelength division multiplexing passive optical networks (WDM-PON) system compatible with wired and 60 GHz band wireless transmission by implementing two-band modulation with a single Mach-Zehnder modulator as parallel phase modulators. In this paper, broadband millimeter wave generation, which is compliant with the ECMA 387 standard, and 2.5 Gbps baseband transmission, which feeds up the requirement of fiber-to-the-home, are simultaneously realized after 25 km long optical fiber transmission. Furthermore, the interference between RF and baseband modulations is theoretically and experimentally investigated. The RF modulation impacts to the baseband signal for different RF modulation formats are deeply investigated. View full abstract»

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  • Energy and Entropy Flow in Erbium-Doped Fiber Amplifiers: A Thermodynamic Approach

    Publication Year: 2012 , Page(s): 2832 - 2838
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1258 KB) |  | HTML iconHTML  

    Current high-capacity and long-reach optical fiber links would not be possible without optical amplification. Especially the use of erbium-doped fiber amplifiers (EDFAs) has revolutionized optical communication systems during the last two decades. Although the amplification process and various effects occurring in rare earth doped amplifiers have been already well understood and accurately modeled, evolution of thermodynamic entropy and other thermodynamic aspects have not been sufficiently considered in the past. This paper analyzes the amplification process in EDFA from the thermodynamic point of view and proposes a novel modeling approach to evaluate both energy and entropy dynamics. The model is described in detail and some exemplary numerical results are presented. View full abstract»

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  • Improvement of Intensity-Modulated Signal With Feed-Forward Control

    Publication Year: 2012 , Page(s): 2839 - 2845
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (570 KB) |  | HTML iconHTML  

    In fiber transmission systems, optical signals can be degraded by noise light such as amplified spontaneous emission from optical amplifiers and coherent crosstalk light leaking from other channels due to imperfections in switches and/or filters in photonic network nodes. In this paper, we propose a feed-forward control circuit that mitigates such signal degradation in intensity-modulated signals. Our scheme is an optical/electrical hybrid circuit consisting of an optical coupler, photo-detector, and Mach-Zehnder intensity modulator (MZ-mod). The transmissivity of the MZ-mod is used to suppress fluctuations in the ??on?? signal state. In addition, the proposed circuit also improves the extinction ratio by adjusting the operating conditions. View full abstract»

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  • Error-Correction Coded Orbital-Angular-Momentum Modulation for FSO Channels Affected by Turbulence

    Publication Year: 2012 , Page(s): 2846 - 2852
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1454 KB) |  | HTML iconHTML  

    The performance of LDPC-precoded, orbital-angular-momentum (OAM) modulation is studied over a 1-km free-space laser communication link subject to OAM modal crosstalk induced by atmospheric turbulence. The multidimensional signal constellation is designed as the Cartesian product of a one-dimensional non-negative pulse-amplitude modulation and a set of orthogonal OAM modes. We evaluate the performance of this modulation scheme by first determining conditional probability density functions (PDFs) of the modal crosstalk for each symbol, resulting from the propagation in weak turbulence using a numerical propagation model. It is observed that OAM modulation is more sensitive to atmospheric turbulence as the number of dimensions increases. However, this can be efficiently mitigated by an error-correction code. The coded OAM modulation scheme provides an energy-efficient alternative to single-mode transmission, since a larger rate can be obtained per given bandwidth. View full abstract»

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  • All-InGaN Phosphorless White Light Emitting Diodes: An Efficiency Estimation

    Publication Year: 2012 , Page(s): 2853 - 2862
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1549 KB) |  | HTML iconHTML  

    In this theoretical study we investigate the efficiency potential of monolithic white light emitting diodes (LEDs) that are free of wavelength-converting phosphors and are based solely on the InGaN material system. For that purpose we develop a numerical model that handles multiple active layers of different emission wavelength and takes photon reabsorption and -emission as well as internal non-radiative and optical losses into account. It is applied both to thin film structures as well as novel nanorod LEDs featuring disc-like active layers. In both cases, the active layers may either consist of multiple thin quantum wells or a single thick, bulk-like InGaN layer. View full abstract»

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  • An Efficient Implementation of Modified Regularized Sparse Recovery for Real-Time Optical Power Monitoring

    Publication Year: 2012 , Page(s): 2863 - 2869
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1057 KB) |  | HTML iconHTML  

    The regularized sparse recovery (RSR) method proposed for optical power monitoring (OPM) has high performance in practice. However, due to its implementation based on interior point method (IPM), it has high computational complexity for real-time OPM system, especially when the number of monitored channels is large. In this paper, we modify the RSR method and propose an efficient implementation of the modified RSR based on the separable surrogate functions (SSF) technique. The resulting algorithm can be realized by simple hardware structure with low computational complexity. Simulation results confirm that accurate and fast optical power spectrum estimation can be achieved with a low-cost tunable optical filter (TOF) by using the proposed method. View full abstract»

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  • Fabrication of a Multimode Interference Device in a Low-Loss Flat-Fiber Platform Using Physical Micromachining Technique

    Publication Year: 2012 , Page(s): 2870 - 2875
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (756 KB) |  | HTML iconHTML  

    A physical micromachining technique is demonstrated in a low-loss flat-fiber substrate to fabricate a multimode interference (MMI) device. The flat-fiber substrate is a low-index-contrast material; however, by making use of two physically micromachined trenches, lateral confinement is achieved providing high index contrast for the MMI region. A 1 ?? 3 MMI device exhibiting 1.89 dB of excess loss has been demonstrated. View full abstract»

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  • Energy-Efficient High-Capacity Optical CDMA Networks by Low-Weight Large Code-Set MPC

    Publication Year: 2012 , Page(s): 2876 - 2883
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1188 KB) |  | HTML iconHTML  

    In this paper, we have proposed a novel spreading code-set based on the prime code families, hereby referred to as transposed sparse-padded modified prime code for synchronous optical code-division multiple-access (OCDMA) networks. The proposed code-set is compared with modified prime codes (MPCs) in terms of correlation properties, bit-error rate (BER), and cardinality. This new low-weight large code-set has better correlation characteristics as compared with MPC families and, as results indicated, the new code-set has considerably improved the BER and power consumption of the OCDMA networks. We have analyzed the performance of the proposed code-set in both incoherent ON-OFF keying and pulse position modulation OCDMA systems, while the multiple access interference was the major degrading quality. The results indicate that at the BER floor of 10-9, the proposed code-set can accommodate greater number of users and consume less power as compared with the MPC under the same transmission conditions. View full abstract»

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  • Increasing Tolerance in Passive Integrated Optical Polarization Converters

    Publication Year: 2012 , Page(s): 2884 - 2889
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (541 KB) |  | HTML iconHTML  

    Integration of optical functions promises to be an important new technology, with applications in telecommunications, datacommunications, and sensing. Controlling the polarization in integrated circuits is needed to fully benefit from the use of light. Integrated polarization converters are required for this, but devices proposed so far have suffered from tight fabrication tolerances. It is shown here what the root of this intolerance is and how critical fabrication errors can be compensated in a two-section polarization converter. The new device leads to doubling of the fabrication tolerances and wavelength range and promises conversion efficiencies above 99% over a wide range of fabrication and operation parameters. View full abstract»

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  • Optical Hexadecimal Coding/Decoding Using 16-QAM Signal and FWM in HNLFs

    Publication Year: 2012 , Page(s): 2890 - 2900
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2206 KB) |  | HTML iconHTML  

    We propose a simple approach to manipulating the constellation of a multilevel modulation signal in the optical domain. By exploiting degenerate four-wave mixing (FWM) in highly nonlinear fibers and adopting 16-ary quadrature amplitude modulation (16-QAM) signal, we demonstrate 10-Gbaud/s optical variable symbol-wise hexadecimal coding/decoding assisted by a continuous-wave (CW) pump or a phase-modulated pump. The former takes the coding through the phase conjugation of degenerate FWM, and the latter offers enhanced coding via the combined contributions from the phase modulation of the pump and the phase-conjugated FWM. The penalty of optical signal-to-noise ratio for coding/decoding is measured to be {< }1.1 dB with a CW pump and {< }1.2 dB with a (0, \pi/4) phase-modulated pump at a bit-error rate of 2e-3 (enhanced forward error correction threshold). The dependence of coding/decoding performance on the phase modulation depth of the pump and the signal/pump misalignment is also investigated. Moreover, considering that a hexadecimal number denotes four binary numbers, we develop the symbol-wise hexadecimal coding/decoding to general binary coding/decoding, i.e., 10-Gbaud/s symbol-wise hexadecimal coding/decoding is accompanied by 40-Gbit/s binary coding/ decoding. View full abstract»

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  • Intensity-Interrogated Sensor Based on Cascaded Fabry–Perot Laser and Microring Resonator

    Publication Year: 2012 , Page(s): 2901 - 2906
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1002 KB) |  | HTML iconHTML  

    A highly sensitive integrated optical biosensor based on the cascade of a Fabry-Perot cavity laser and a microring resonator is investigated theoretically and experimentally. The free spectral ranges of the microring and the laser cavity are designed to be about the same in order to apply intensity interrogation. The variation of the refractive index of the fluidic sample results in a large shift in the envelope function of the total transmission spectrum of the sensor, and consequently, a large change in the transmitted power. The simple light-source-integrated sensing scheme achieved a high sensitivity of 1000 dB/RIU in the preliminary experiment, demonstrating its principle and potential for low-cost practical applications. 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