Optically preamplified receiver performance due to VSB filtering for 40-Gb/s optical signals modulated with various formats

Optically preamplified receiver performance according to the vestigial sideband (VSB) filtering has been numerically investigated for 40-Gb/s optical signals modulated with nonreturn-to-zero, duobinary nonreturn-to-zero (NRZ), return-to-zero (RZ), carrier-suppressed RZ, and duobinary carrier-suppressed RZ formats. The VSB filtering enables the spectral widths of NRZ, duobinary NRZ, and RZ signals to be reduced without severe power penalties at the receiver. On the other hand, carrier-suppressed RZ and duobinary carrier-suppressed RZ signals have no large advantages over VSB filtering because of the characteristics of their signals. Our results suggest that RZ signals are the most suitable modulation format for VSB filtering, without considering the filter loss, because of the tolerance of the intersymbol interference and a large spectral width. However, duobinary NRZ signals are the most suitable modulation format for VSB filtering, considering the filter loss, because of their narrow spectral width.     

Transmission performance of 10-Gb/s 1550-nm transmitters using semiconductor optical amplifiers as booster amplifiers

We have demonstrated the transmission performance of 10-Gb/s transmitters based on LiNbO/sub 3/ modulator using semiconductor optical amplifiers (SOAs) as booster amplifiers. Utilizing the negative chirp converted in SOAs and self-phase modulation induced by high optical power, we can successfully transmit 10-Gb/s optical signals over 80 km through the standard single-mode fiber with the transmitter using SOAs as booster amplifiers. SOAs can be used for booster amplifiers with a careful adjustment of the operating conditions. In order to further understand an SOA's characteristics as a booster amplifier, we model SOAs and other subsystems to verify the experimental results. Based on the good agreement between the experimental and simulation results, we can find the appropriate parameters of input signals for SOAs, such as extinction ratio, rising/falling time, and chirp parameter to maximize output dynamic range and available maximum output power (P/sub o,max/).     

Validation of 3-D curved objects: CAD model and fabricatedworkpiece

This paper proposes a new method to describe and identify a 3-D curved object for the purpose of validating a fabricated object to the design specification. Curved 3-D objects are, in general, difficult to represent and identify because they lack distinct properties such as edges, planes, or cylindrical surfaces which are the building blocks in representing objects. In this paper, the authors propose to use principal axes of a 3-D object to establish a reference for the representation. A method of obtaining an inertia matrix from a 3-D range image is developed. The unique set of principal axes is obtained from the inertia matrix of an object with an arbitrary 3-D position and orientation, and the object can be described uniquely on these principal axes. On the principal axes, an object is described by a set of features describing the shape of the object such as spine, section size, section orientation, and section contraction. The features are used for comparing two objects for the validation purpose. The authors also propose a direct measure of similarity between two objects as a mean-squared difference of radii. As an experiment, two 3-D object models are designed through a CAD package, and fabricated objects are compared with the designed models for validation purposes     

Evaluation of transmission performance in cost-effective optical duobinary transmission utilizing modulator''s bandwidth or low-pass filter implemented by a single capacitor

We have investigated cost-effective and simple duobinary modulations with/without using low pass filters (LPF) for the conventional duobinary modulation. For the proposed schemes, the effects of the electrical bandwidth and the DC extinction ratio of Mach–Zehnder (MZ) modulators have been investigated for transmission performances. The calculated eye-diagrams and BER characteristics of the proposed schemes have similar characteristics at 160 km transmission, compared to the conventional duobinary scheme. To explain the transmission performance of the proposed schemes, the chirp characteristics have been compared. We have obtained a similar SPM tolerance between the proposed schemes and the conventional duobinary modulation scheme.     

Theoretical investigation of optical wavelength conversion techniques for DPSK Modulation formats using FWM in SOAs and frequency comb in 10 gb/s transmission systems

We have investigated the wavelength conversion techniques for differential phase-shift keying (DPSK) modulation formats in 10 Gb/s transmission systems, compared with the non-return-to-zero (NRZ) modulation format. For the wavelength conversion of DPSK modulation formats, we employed the wavelength converters based on the four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) and the frequency comb generated by phase modulation. The power penalty at 10/sup -9/ bit error rate was used as a measure of the system performance degraded by the wavelength conversion. Our simulation results show that the DPSK modulation formats have a smaller power penalty than the NRZ modulation format for the wavelength conversion using the FWM effect in an SOA due to a much lower pattern effect. However, as the wavelength conversion uses the frequency comb generated by phase modulation, it has a similar power penalty compared with the NRZ modulation format. It is also shown that the DPSK modulation formats are possible to obtain the power penalty less than 0.4 dB for both wavelength conversion techniques.     

Autonomous collision detection and avoidance for ARAGON USV: Development and field tests

This study addresses the development of algorithms for multiple target detection and tracking in the framework of sensor fusion and its application to autonomous navigation and collision avoidance systems for the unmanned surface vehicle (USV) Aragon. To provide autonomous navigation capabilities, various perception sensors such as radar, lidar, and cameras have been mounted on the USV platform and automatic ship detection algorithms are applied to the sensor measurements. The relative position information between the USV and nearby objects is obtained to estimate the motion of the target objects in a sensor‐level tracking filter. The estimated motion information from the individual tracking filters is then combined in a central‐level fusion tracker to achieve persistent and reliable target tracking performance. For automatic ship collision avoidance, the combined track data are used as obstacle information, and appropriate collision avoidance maneuvers are designed and executed in accordance with the international regulations for preventing collisions at sea (COLREGs). In this paper, the development processes of the vehicle platform and the autonomous navigation algorithms are described, and the results of field experiments are presented and discussed.     

Feasibility and Optimization of 1-TTI-Based Full-Duplex Two-Way Relay System

Wireless Personal Communications - Maximizing system capacity is one of the major concerns in inband full-duplex (IFD) two-way relay (TWR) system using analog network coding (ANC). This paper...     

Facile synthesis of fully ordered L10-FePt nanoparticles with controlled Pt-shell thicknesses for electrocatalysis

We report a simple one-step approach for the synthesis of ～4 nm uniform and fully L10-ordered face-centered tetragonal (fct) FePt nanopartides (NPs) embedded in ～60 nm MCM-41 (fct-FePt NPs@MCM-41).We controlled the Pt-shell thickness of the fct-FePt NPs by treating the fct-FePt NPs@MCM-41 with acetic acid (HOAc) or hydrochloric acid (HC1) under sonication,thereby etching the surface Fe atoms of the NPs.The fct-FePt NPs deposited onto the carbon support (fct-FePt NP/C) were prepared by mixing the fct-FePt NPs@MCM-41 with carbon and subsequently removing the MCM-41 using NaOH.We also developed a facile method to synthesize acid-treated fct-FePt NP/C by using a HF solution for simultaneous surface-Fe etching and MCM-41 removal.We studied the effects of both surface-Fe etching and Pt-shell thickness on the electrocatalytic properties of fct-FePt NPs for the methanol oxidation reaction (MOR).Compared with the non-treated fct-FePt NP/C catalyst,the HOAc-treated and HCl-treated catalysts exhibit up to 34％ larger electrochemically active surface areas (ECASAs);in addition,the HCl-treated fct-FePt NP (with ～1.0 nm Pt shell)/C catalyst exhibits the highest specific activity.The HF-treated fct-FePt NP/C exhibits an ECASA almost 2 times larger than those of the other acid-treated fct-FePt NP/C catalysts and shows the highest mass activity (1,435 mA.mg~,2.3 times higher than that of the commercial Pt/C catalyst) and stability among the catalysts tested.Our findings demonstrate that the surface-Fe etching for the generation of the Pt shell on fct-FePt NPs and the Pt-shell thickness can be factors for optimizing the electrocatalysis of the MOR.     

Preparation of magnetic ion‐exchange resins by the suspension polymerization of styrene with magnetite

Magnetic polymer microspheres composed of magnetite, styrene, and divinylbenzene were prepared by suspension polymerization to produce magnetic ion‐exchange resins (MIEXs). The magnetite was grafted with oleic acid to improve the magnetic properties of the MIEXs and to prevent the magnetite from flushing out of the MIEXs. The shape and magnetic properties of the magnetic microspheres were investigated with scanning electron microscopy and vibrating‐sample magnetometry. The average diameter of the prepared magnetic polymer microspheres was about 219 μm. The two types of MIEXs were prepared, magnetic cation‐exchange resins (MCEXs) and magnetic anion‐exchange resins (MAEXs). MCEX was prepared by sulfonation of magnetic polymer microspheres, and MAEX was made by a quaternization reaction with triethylamine of chloromethylated magnetic polymer microspheres. With diffuse‐reflectance Fourier transform infrared spectroscopy, elemental analysis, and acid–base titration, the degree of substitution and ion‐exchange capacity of the MIEXs were assessed. The efficiency of each MCEX and MAEX for the purification of contaminated water was examined with Co²⁺ and NO solutions, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2058–2067, 2003     

Adaptive Resource Allocation for Uplink Carrier Aggregation Scheme in LTE‐A‐Type Networks

Carrier aggregation is an essential feature in the Long Term Evolution‐Advanced (LTE‐A) system, which allows the scalable expansion of the effective bandwidth to be delivered to user equipment (UE) through the concurrent use of radio resources across multiple component carriers (CCs). This system's optimal radio‐resource use has received much attention under simultaneous access (SA) scenarios for multiple CCs (m‐CCs). This letter establishes how many CCs a UE should simultaneously connect to maintain maximum uplink capacity. Under the m‐CC LTE‐A system, the spectral efficiency of the m‐CC SA scheme (m≥2) is compared with that of CC selection (CCS). Numerical results reveal that the 2‐CC SA scheme outperforms CCS and performs almost equally to the m‐CC SA scheme (m≥3).