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Lightwave Technology, Journal of

Issue 15 • Date Aug.1, 2014

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Displaying Results 1 - 21 of 21
  • [Front cover]

    Page(s): C1
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  • Journal of Lightwave Technology publication information

    Page(s): C2
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  • Table of contents

    Page(s): 2595 - 2596
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  • Multihop Free-Space Optical Communications Over Turbulence Channels with Pointing Errors using Heterodyne Detection

    Page(s): 2597 - 2604
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (478 KB) |  | HTML iconHTML  

    This paper proposes and analyzes the performance of the multihop free-space optical (FSO) communication links using a heterodyne differential phase-shift keying modulation scheme operating over a turbulence induced fading channel. A novel statistical fading channel model for multihop FSO systems using channel-state-information-assisted and fixed-gain relays is developed incorporating the atmospheric turbulence, pointing errors, and path-loss effects. The closed-form expressions for the moment generating function, probability density function, and cumulative distribution function of the multihop FSO channel are derived using Meijer's G-function. They are then used to derive the fundamental limits of the outage probability and average symbol error rate. Results confirm the performance loss as a function of the number of hops. Effects of the turbulence strength varying from weak-to-moderate and moderate-to-strong turbulence, geometric loss, and pointing errors are studied. The pointing errors can be mitigated by widening the beam at the expense of the received power level, whereas narrowing the beam can reduce the geometric loss at the cost of increased misalignment effects. View full abstract»

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  • All-Optical DPSK Regenerative One-to-Nine Wavelength Multicasting Using Dual-Pump Degenerate Phase Sensitive Amplifier

    Page(s): 2605 - 2612
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB) |  | HTML iconHTML  

    We present theoretical investigation of all-optical differential phase-shift keying (DPSK) regenerative wavelength multicasting using dual-pump degenerate phase sensitive amplifier (PSA), based on seven-wave model rather than traditional three-wave model. We first test the accuracy of the seven-wave model in the context of 40 Gb/s DPSK all-optical regenerative multicasting. We find that the seven-wave model is more accurate than the three-wave model. Meanwhile, we successfully optimize optical signal power, frequency spacing between two pumps, and regeneration capability of all multicasting channels. All-optical DPSK regenerative one-to-nine wavelength multicasting can be successfully realized. Both eye diagrams and the calculated bit error rate curve demonstrate that the optical signal to noise ratio penalties of all multicasting channels are improved by around 3 dB. Finally, to the best of our knowledge, we investigate, for the first time, the effects of the high-order four-wave mixing (FWM) products on the evolution of pump-to-signal intensity modulation transfer (IMT) and IMT from the pump to all wavelength-multicasting channels in a dual-pump degenerate PSA. We find that high-order FWM products contribute to the suppression of pump-to-signal IMT after proper optimization of dual-pump's frequency spacing and signal optical power. Both regenerative one-to-nine wavelength multicasting and pump-to-signal IMT smaller than 1 can be simultaneously achieved under the gain saturation region. View full abstract»

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  • Scheduling Hybrid WDM/TDM Ethernet Passive Optical Networks Using Modified Stable Matching Algorithm

    Page(s): 2613 - 2622
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1114 KB) |  | HTML iconHTML  

    Hybrid wavelength division multiplexing/time division multiplexing (WDM/TDM) scheduling in multi-channel Ethernet passive optical networks (EPON) is gaining popularity compared to its only TDM or only WDM counterpart as they provide more flexibility, energy efficient load distribution and increased number of users and bandwidth support. In this paper, we have summarized the existing proposals for multi-channel EPON and proposed a novel scheme to further enhance the scheduling efficiency. For that purpose, a Modified Stable Matching Algorithm (MSMA) has been developed. We have also introduced a predictive just-in-time scheduling framework to dynamically evoke the MSMA in real time. We have provided extensive simulation results to prove the effectiveness of our proposed scheduling scheme compared to other existing schemes. View full abstract»

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  • Direct Synthesis of 2-D Coupled Microring Resonator Filter Networks

    Page(s): 2623 - 2628
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (371 KB) |  | HTML iconHTML  

    We present a method for directly synthesizing coupled microring resonator filter networks of general 2-D coupling topologies. The method is based on the “energy coupling in time” formalism of systems of microring resonators and can be used to synthesize optical filter transfer functions in the s-domain. An example of a class of microring filters with equiripples in both the amplitude and group delay responses is also given to illustrate the application of the method to the design of complex microring filter architectures. View full abstract»

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  • Secure OFDM-PON System Based on Chaos and Fractional Fourier Transform Techniques

    Page(s): 2629 - 2635
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3275 KB) |  | HTML iconHTML  

    We propose a novel method to simultaneously improve the physical layer security and the transmission performance of the orthogonal frequency division multiplexing (OFDM) passive optical network system by using chaos and fractional Fourier transform (FrFT) techniques. The designed 3-D chaotic sequences are used to form the training sequence for time synchronization, to perform the OFDM subcarriers masking, and to control the fractional order of the FrFT operation. The analyses show that the whole key space size of the proposed scheme could be beyond 1050, and the peak-to-average-power-ratio of the transmitted OFDM signal can be decreased by about 0.5 dB. Furthermore, we successfully demonstrate an 8.18 Gbps 16-quadrature-amplitude- modulation (QAM)-OFDM data transmission experiment with chaotic and FrFT operations over 25 km single mode fiber. The results show that the proposed scheme could effectively enhance the system security and the transmission performance without additional bandwidth requirement. View full abstract»

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  • ACP-OPLL Performance in Presence of Out-of-Band Interference

    Page(s): 2636 - 2642
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    Nonlinear dynamics inside an optical phase locked loop (OPLL) were studied to determine their effect on the OPLL performance in radar front end applications. An improved theoretical model of the OPLL was presented. Numeric simulations were performed to study the OPLL performance penalties in presence of external interference and its dynamic behavior during phase tracking failure. These results were validated by experimental observations. View full abstract»

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  • Experimental and Numerical Analysis of p-Electrode Patterns on the Lateral GaN-Based LEDs

    Page(s): 2643 - 2648
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (639 KB) |  | HTML iconHTML  

    Many studies have introduced electrode patterns to improve current crowding and enhance the light output power of LEDs. This study conducted experimental and numerical analysis to investigate the influence of electrode design on the luminous efficiency of LEDs. An extended p-electrode was used to relieve current crowding commonly encountered at the edge of conventional electrodes. Unfortunately, an extension of the p-electrode obscures light emitted from the active layer. Therefore, we fabricated arrays of holes, 3 or 5 μm in diameter, on the electrodes and compared their effectiveness in enhancing light output efficiency. Optical measurements demonstrated that increasing the diameter of the holes led to an increase in light output power. The maximum output power of the proposed LED was 48.1 mW for an array of 5 μm holes, which is higher than that of 43.8 mW for the conventional LED. At a current injection of 500 mA, the output power of the proposed LED (5 μm holes) was 47.7 mW, which is nearly double that of conventional LED (23.7 mW). Numerical analysis was also used to simulate the distribution of current density in the active layer of the LEDs. The relationship between current spreading length and internal quantum efficiency were used to calculate the distribution of luminous intensity. Further modeling was performed to simulate light output power via Monte Carlo ray tracing. The results of numerical simulation are in strong agreement with those obtained from experiments. View full abstract»

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  • Performance Analysis of Multirate Multiservice Optical CDMA Networks Adopting Overlapping PPM Signaling

    Page(s): 2649 - 2658
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1258 KB) |  | HTML iconHTML  

    In this paper, an optical code-division multiple-access (OCDMA) system employing overlapping pulse-position modulation (OPPM) is proposed to support multimedia services with different bit-rate and quality-of-service (QoS) requirements in OCDMA networks. Both wrapped OPPM (WOPPM) and unwrapped OPPM (UOPPM) are considered. The proposed system achieves multirate and multi-QoS transmission by using multilength variable-weight optical orthogonal codes (MLVW-OOCs) as signature sequences and using different values of OPPM modulation parameters. Furthermore, numerical analysis is performed for two different receiver structures, namely, correlation receivers with and without hard-limiters. In our analysis, the multiple-access interference (MAI) is considered as the main performance limiting factor. In addition, the performance of the proposed system is evaluated and compared to that of traditional OOK-OCDMA system. Our results reveal that under both pulsewidth and throughput constraints, the performances of the proposed WOPPM- and UOPPM-OCDMA systems are significantly superior to that of OOK-OCDMA system. View full abstract»

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  • A Circuit Model for Analysis of Metal–Insulator–Metal Plasmonic Complementary Split-Ring Resonators

    Page(s): 2659 - 2665
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    A circuit model based on the transmission line theory is proposed to analyze the recently introduced metal-insulator-metal (MIM) complementary split-ring resonators (CSRRs). It is shown that integer and noninteger modes of CSRRs can be characterized by transmission line models with short- and open-circuited terminals. The proposed circuit model is then extended to incorporate side-coupling effects between the CSRRs and straight MIM waveguides. Thereby, simple closed-form expressions are provided for the coupling quality factor. It is shown that waveguide resonator structures based on CSRRs at specific resonance frequency and bandwidth can be smaller than waveguide resonator structures based on conventional ring resonators. Thanks to the smaller size of CSRRs, the coupling in the former arrangement is stronger than it is in the latter. Therefore, CSRRs are not required to be in the extreme proximity of the waveguide as in the waveguide ring resonators. View full abstract»

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  • Relation of Refractive Index Change to Ti-Concentration in Ti-Diffused LiNbO3 Waveguide Doped With Sc3+

    Page(s): 2666 - 2670
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    Multimode Ti4+-diffused LiNbO3 planar waveguide doped with Sc3+ ions was fabricated by codiffusion of stacked Sc2O3 and Ti-metal thin film coated onto Z-cut congruent LiNbO3 substrate at 1060 °C in wet O2. The Ti4+-concentration was profiled by secondary ion mass spectrometry. The refractive index profile is constructed from measured mode index, and correlated with the Ti4+ profile. Other two related issues including the contribution of Sc3+-doping to substrate refractive index and Li2O out-diffusion were also studied. The results show that the Sc3+-doping has little contribution to the substrate index and the Li2O out-diffusion was effectively suppressed. The index change and Ti 4+-concentration follow an exponential relationship with a power index 0.54/0.79 for the ordinary/extraordinary ray. The relationship is similar to that of conventional Ti:LiNbO3 waveguide because of little contribution of Sc3+-doping to the substrate index and effective suppression for Li2O out-diffusion. Some considerations for fabricating an optical-damage-resistant Ti:Sc:LiNbO3 waveguide are given. View full abstract»

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  • Bit Error Rate Measurements of All-Optical Flip-Flop Operations of a 1.55-μm Polarization Bistable VCSEL

    Page(s): 2671 - 2677
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (837 KB) |  | HTML iconHTML  

    We measured the bit error rate (BER) of all-optical flip-flop operations using a 1.55-μm polarization bistable vertical-cavity surface-emitting laser (VCSEL). Polarization bistable flip-flop operations were obtained by injecting optical set and reset pulses with independently adjusted wavelengths toward the two VCSEL lasing modes, whose polarizations are orthogonal to each other. Acquired waveforms showed clearly opened eyes, and BERs less than 1 × 10-9 were measured up to 1 Gb/s although the optical set and reset pulse power was much lower than the VCSEL output power. We also demonstrated all-optical flip-flop operations by injecting optical set and reset pulses with the same wavelength, which were generated by a single laser diode. In this case, we obtained polarization bistable flip-flop operations up to 500 Mb/s with almost the same BER values that were obtained when the wavelengths of the set and reset pulses were adjusted independently. The optical input pulse powers were higher than for the case using input pulses with two different wavelengths, but still lower than the VCSEL output power. View full abstract»

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  • Theoretical Considerations in Designing Ultra-High Speed All-Optical Clock Recovery Using Fiber Optical Parametric Amplifiers

    Page(s): 2678 - 2689
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    In this paper, a new all-optical phase-locked loop (OPLL) in a TDM system is proposed and analyzed. The scheme relies on using fiber optical parametric amplifier (FOPA) device models and theories. In the proposed OPLL, the local clock pulse stream and the received data signal pulses are fed into the FOPA as its pump and amplified signals, respectively. The power of the resulting, relatively, strong idler signal depends on the phase difference between the local clock and the received data signal pulses, and it is used to reveal the OPLL's error signal. We characterize the mathematical structure of the proposed OPLL and identify its three intrinsic sources of phase noises namely, randomness of received data pulses, detector's shot noise, and the FOPA noises such as amplified spontaneous emission (ASE). The ASE noise is reflected in the FOPA's noise figure parametrically. However, the effects of the other two noise sources on the proposed OPLL performance are investigated, using the power spectral densities (PSDs) of the signals involved in the OPLL. Finally, the PSDs are used to obtain a mathematical expression for the OPLL's timing jitter. From the analytical results, our proposed OPLL benefits from the FOPA's inherent large bandwidth and exhibits a very low timing jitter, which is in the order of femtosecond, for an OTDM system with 80 Gbps data rate. View full abstract»

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  • Nonlinearity Cancellation in Fiber Optic Links Based on Frequency Referenced Carriers

    Page(s): 2690 - 2698
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    We study the limitations and their origins in the nonlinear effects mitigation in fiber-optic communication systems. The carrier frequencies uncertainty and their stochastic variations are identified as the major impeding factor for successful inter-channel nonlinear impairments management. Furthermore, the results clearly point out to the significant benefits of employing fully frequency referenced carriers in transmission, with frequency combs representing an immediately available solution. Finally, frequency referenced transmitters and/or receivers are shown as critical for availing longer reach at high spectral efficiencies in transmission. View full abstract»

    Open Access
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    Page(s): B2699 - B2700
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  • Open Access Publishing

    Page(s): 2701
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  • IEEE Xplore Digital Library

    Page(s): 2702
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  • Journal of Lightwave Technology information for authors

    Page(s): C3
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  • [Blank page - back cover]

    Page(s): C4
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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.

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Meet Our Editors

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