Most existing outlier detection algorithms only utilized location of trajectory points and neglected some important factors such as speed, acceleration, and corner. To address this problem, we present a Trajectory Outlier Detection algorithm based on Multi-Factors (TODMF). TODMF is improved in terms of distance-based outlier detection algorithms. It combines multi-factors into outlier detection to find more meaningful trajectory outliers. We resort to Canonical Correlation Analysis (CCA) to optimize the number of factors when determining what factors will be considered. Finally, the experiments with real trajectory data sets show that TODMF performs efficiently and effectively when applied to the problem of trajectory outlier detection.

Recent progress in research on the finite element method (FEM) for optical waveguide design and analysis is reviewed, focusing on the author's works. After briefly reviewing fundamentals of FEM such as a theoretical framework, a conventional nodal element, a newly developed edge element to eliminate nonphysical, spurious solutions, and a perfectly matched layer to avoid undesirable reflections from computational window edges, various FEM techniques for a guided-mode analysis, a beam propagation analysis, and a waveguide discontinuity analysis are described. Some design examples are introduced, including current research activities on multi-core fibers.

An optoelectronic 32-bit serial-to-parallel converter with a novel conversion scheme and shared-trigger configuration has been developed for the label processing of 100-Gbps (25-Gbps $ imes 4 lambda)$ optical packets. No external optical trigger source is required to operate the converter, as the optical packet itself is used to perform self-triggering. Compared to prior optoelectronic label converters, the new device has a much higher gain even while converting labels at higher data rates, and exhibits tolerance to the voltage swing of received packets. The device response is presented together with the experimental demonstration of serial-to-parallel conversion for 4 different labels at 25 Gbps.

In this paper, the function expansion based topology optimization is employed to the automatic optimization of the waveguide dispersion property, and the optimum design of low-dispersion slow-light photonic crystal waveguides is demonstrated. In order to realize low-dispersion and large group index, an objective function to be optimized is expressed by the weighted sum of the objective functions for the desired group index and the low-dispersion property, and weighting coefficients are updated through the optimization process.

Transmit diversity generally requires more than one antenna at the transmitter. However, many wireless devices are limited by size or hardware complexity. Cooperative diversity techniques were proposed to overcome this limitation. Cooperative communication has been widely investigated to improve the performance of wireless communication. Unfortunately, most existing cooperative schemes have the common fault of decreased transmission rate because the destination should receive the decodable compositions of symbols from the source and the relay. In this letter, we propose a new cooperative model that uses spatial phase coding (SPC) for orthogonal frequency division multiple access (OFDMA). This technique is free from the rate-loss and allows seamless cooperative communication while its diversity gain matches that of the conventional multiple antenna technique. The proposed technique is evaluated in terms of bit error rate (BER) and simulation results show that the proposed cooperative scheme approaches the performance of conventional multiple antenna system when the link between users is guaranteed.

For next generation planar lightwave circuit (PLC) devices, high function and high-density integration are required as well as downsizing and cost reduction. To realize these needs, high refractive index difference between a core and a clad $(Delta)$ is required. To use PLC for practical applications, silica-based PLC is one of the most attractive candidate. However, degradation of the optical properties and productivity occur when $Delta$ of the core becomes high. Thus, $Delta$ of most of the conventional PLC with GeO$_2$-SiO$_2$ core is designed less than 2.5%. In this paper, we report a silica-based ultra-high $Delta $ PLC with ZrO$_2$-SiO$_2$ core. 5.5%-$Delta$ ZrO$_2$-SiO$_2$ PLC has been realized with low propagation loss and basic characteristics has been confirmed. Potential of chip size reduction of the ZrO$_2$-SiO$_2$ PLC is shown.

We describe wavelength-routed switching technology for 25-Gbit/s optical packets using a tunable transmitter that monolithically integrates a parallel-ring-resonator tunable laser and an InGaAlAs electro-absorption modulator (EAM). The transmitter provided accurate wavelength tunability with 100-GHz spacing and small output power variation. A 25-Gbit/s burst-mode optical-packet data was encoded onto the laser output by modulating the integrated EAM with a constant voltage swing of 2 V at 45$^{circ}$C. Clear eye openings were observed at the output of the 100 GHz-spaced arrayed-waveguide grating with error-free operation being achieved for all packets. The tunable transmitter is very promising for realizing a high-speed, large-port-count and energy-efficient wavelength-routing switch that enables the forwarding of 100-Gbit/s optical packets.

We investigate resolution improvement in optical quantization with keeping high sampling rate performance in optical sampling. Since our optical quantization approach uses power-to-wavelength conversion based on soliton self-frequency shift, a spectral compression can improve resolution in exchange for sampling rate degradation. In this work, we propose a different approach for resolution improvement by parallel use of dispersion devices so as to avoid sampling rate degradation. Additional use of different dispersion devices can assist the wavelength separation ability of an original dispersion device. We demonstrate the principle of resolution improvement in 3 bit optical quantization. Simulation results based on experimental evaluation of 3 bit optical quantization system shows 4 bit optical quantization is achieved by parallel use of dispersion devices in 3 bit optical quantization system. The maximum differential non-linearity (DNL) and integral non-linearity (INL) are 0.49 least significant bit (LSB) and 0.50 LSB, respectively. The effective number of bits (ENOB) estimated to 3.62 bit.

Integrated InP polarization converters based on half-ridge structure are studied numerically. We demonstrate that the fabrication tolerance of the half-ridge structure can be extended significantly by introducing a slope at the ridge side and optimizing the thickness of the residual InGaAsP layer. High polarization conversion over 90% is achieved with the broad range of the waveguide width from 705 to 915~nm, corresponding to a factor-of-two or larger improvement in the fabrication tolerance compared with that of the conventional polarization converters. Finally we present a simple fabrication procedure of this newly proposed structure, where the thickness of the residual InGaAsP layer is controlled precisely by using a thin etch-stop layer.

This paper covers new architectures, technologies, and performance benchmarking together with prospects for high productivity and high performance computing enabled by photonics. The exponential and sustained increases in computing and data center needs are driving the demands for exascale computing in the future. Power-efficient and parallel computing with balanced system design is essential for reaching that goal as should support ∼billion total concurrencies and ∼billion core interconnections with ∼exabyte/second bisection bandwidth. Photonic interconnects offer a disruptive technology solution that fundamentally changes the computing architectural design considerations. Optics provide ultra-high throughput, massive parallelism, minimal access latencies, and low power dissipation that remains independent of capacity and distance. In addition to the energy efficiency and many of the fundamental physical problems, optics will bring high productivity computing where programmers can ignore locality between billions of processors and memory where data resides. Repeaterless interconnection links across the entire computing system and all-to-all massively parallel interconnection switch will significantly transform not only the hardware aspects of computing but the way people program and harness the computing capability. This impacts programmability and productivity of computing. Benchmarking and optimization of the configuration of the computing system is very important. Practical and scalable deployment of photonic interconnected computing systems are likely to be aided by emergence of athermal silicon photonics and hybrid integration technologies.

In this paper we summarize the work conducted in our group in the area of E- and W-band optical high-capacity fiber-wireless links. We present performance evaluations of E- and W-band mm-wave signal generation using photonic frequency upconversion employing both VCSELs and ECLs, along with transmission over different type of optical fibers and for a number of values for the wireless link distance. Hybrid wireless-optical links can be composed of mature and resilient technology available off-the-shelf, and provide functionalities that can add value to optical access networks, specifically in mobile backhaul/fronthaul applications, dense distributed antenna systems and fiber-over-radio scenarios.

Graphene is attracting attention in electrical and optical research fields recently. We measured the optical absorption characteristics and polarization dependence of single-layer graphene (SLG) on sub-micrometer Si waveguide. The results for graphene lengths ranging from 2.5 to 200 $mu$ m reveal that the optical absorption by graphene is 0.09 dB/$mu$ m with the TE mode and 0.05 dB/$mu$ m with the TM mode. The absorption in the TE mode is 1.8 times higher than that in the TM mode. An optical spectrum, theoretical analysis and Raman spectrum indicate that surface-plasmon polaritons in graphene support TM mode light propagation.

In this letter, a cooperative scheme is proposed for the broadcasting and cellular communication system. The proposed scheme improves bit error rate (BER) performance and throughput on the edge of a cellular base station (CBS) cooperating with another CBS in the same broadcasting coverage. The proposed scheme for the enhancement of BER performance employs two schemes by a channel quality information (CQI) between a broadcasting base station (BBS) and users. In a physical area, the edge of a CBS is concatenated with the edge of another CBS. When users are on the edge of a CBS, they transmit simultaneously the CQI to CBSs, and then a BBS and CBSs transmit signals by the proposed algorithm. The two schemes apply space-time cyclic delay diversity (CDD) and a combination of space-time block code (STBC) with vertical Bell Laboratories Layered Space-Time (V-BLAST) to a signal from a BBS and CBSs. The resulting performance indicates that the proposed scheme is effective for users on the edges of CBSs.

Substrate noise coupling in RF receiver front-end circuitry for LTE wireless communication was examined by full-chip level simulation and on-chip measurements, with a demonstrator built in a 65nm CMOS technology. A CMOS digital noise emulator injects high-order harmonic noises in a silicon substrate and induces in-band spurious tones in an RF receiver on the same chip through substrate noise interference. A complete simulation flow of full-chip level substrate noise coupling uses a decoupled modeling approach, where substrate noise waveforms drawn with a unified package-chip model of noise source circuits are given to mixed-level simulation of RF chains as noise sensitive circuits. The distribution of substrate noise in a chip and the attenuation with distance are simulated and compared with the measurements. The interference of substrate noise at the 17th harmonics of 124.8MHz — the operating frequency of the CMOS noise emulator creates spurious tones in the communication bandwidth at 2.1GHz.

Wireless body area networks (BANs) are attracting great attention as a future technology of wireless networks for healthcare and medical applications. Wireless BANs can generally be divided into two categories, i.e., wearable BANs and implant BANs. However, the performance requirements and channel propagation characteristics of these two kinds of BANs are quite different from each other, that is, wireless signals are approximately transmitted along the human body as a surface wave in wearable BANs, on the other hand, the signals are transmitted through the human tissues in implant BANs. As an effective solution for this problem, this paper first introduces a dual-mode communication system, which is composed of transmitters for in-body and on-body communications and a receiver for both communications. Then, we evaluate the bit error rate (BER) performance of the dual-mode communication system via computer simulations based on realistic channel models, which can reasonably represent the propagation characteristics of on-body and in-body communications. Finally, we conduct a link budget analysis based on the derived BER performances and discuss the link parameters including system margin, maximum link distance, data rate and required transmit power. Our computer simulation results and analysis results demonstrate the feasibility of the dual-mode communication system in wireless BANs.

This paper presents a 120-GHz-band amplifier module with a hermetic sealing structure for a broadband wireless system. The sealing structure for F-band waveguides is a laminate composed of two sealing plates and a spacer. Each sealing plate has a fused glass window and separates inside air from the ambient atmosphere. The design process of the sealing structure is simple and has good simulation fidelity. The hermetic sealing structure designed for an amplifier in a 120-GHz-band wireless link has an insertion loss of less than 1dB and a return loss of more than 15dB in the operating band. We made three kinds of sealed modules to evaluate the sealing function. The modules sealed with this technique meet the hermetic-seal standard in MIL-STD-883F. We then verified that the sealing structure on the sealed modules has a small enough effect for the transmittance of the intrinsic characteristics. In addition, we performed 10-Gbit/s data transmission using a sealed amplifier module with the bit error rate of less than 10-10.

E-band communication is allocated to the frequency bands of 71-76 and 81-86GHz. Radio-frequency (RF) front-end components for E-band communication have been realized using compound semiconductor technology. To realize a CMOS LNA for E-band communication, we propose a gain-boosted cascode amplifier (GBCA) stage that simultaneously provides high gain and stability. Designing an LNA from scratch requires considerable time because the tuning of matching networks with consideration of the parasitic elements is complicated. In this paper, we model the characteristics of devices including the effects of their parasitic elements. Using these models, an optimizer can estimate the characteristic of a designed LNA precisely without electromagnetic simulations and gives us the design values of an LNA when the layout constraint is ignored. Starting from the values, a four-stage LNA with a GBCA stage is designed very easily even though the layout constraint is considered and fabricated by a 65nm LP CMOS process. The fabricated LNA is measured, and it is confirmed that it achieves 18.5GHz bandwidth and over 24.3dB gain with 50.6mW power consumption. This is the first LNA to achieve a gain bandwidth of over 300GHz in the E-band among the LNAs utilizing any kind of semiconductor technologies. In this paper, we have proved that CMOS technology, which is suitable for baseband and digital circuitry, is applicable to a communication system covering the entire E-band.

A 125MHz 64-phase delay-locked loop (DLL) is implemented for time recovery in a digital wire-line system. The architecture of the proposed DLL comprises a coarse-locking circuit added to a conventional DLL circuit, which consists of a delay line including a bias circuit, phase detector, charge pump, and loop filter. The proposed coarse-locking circuit reduces the locking time of the DLL and prevents harmonic locking, regardless of the duty cycle of the clock. In order to verify the performance of the proposed coarse-locking circuit, a 64-phase DLL with an operating frequency range of 40 to 200MHz is fabricated using a 0.18-µm 1-poly 6-metal CMOS process with a 1.8V supply. The measured rms and peak-to-peak jitter of the output clock are 3.07ps and 21.1ps, respectively. The DNL and INL of the 64-phase output clock are measured to be -0.338/+0.164 LSB and -0.464/+0.171 LSB, respectively, at an operating frequency of 125MHz. The area and power consumption of the implemented DLL are 0.3mm2 and 12.7mW, respectively.

In this paper, we investigate a combination scheme of subcarrier intensity-modulation (SIM) with spatial modulation (SM) for optical wireless communication. Using computer simulation, the performances of the proposed SIM/SM scheme are investigated and compared with those of the conventional SIM scheme in the additive white gaussian noise (AWGN) as well as in outdoor environment with turbulence induced fading characteristics. Numerical results show that the proposed SIM/SM scheme can outperform the conventional SIM in an environment with different spectral efficiencies. When the spectral efficiency is varied from 2bits/s/Hz to 4bits/s/Hz, an Eb/N0 gain of 2dB to 5dB is achieved, when the bit error rate of 10-5 is maintained. It shows that the employment of SM may further improve the power efficiency of SIM, when the number of subcarriers increases according to the spectral efficiency. When the spectral efficiency is 4bits/s/Hz, the SIM/SM scheme for 0.5 of log-irradiance variance in the log-normal turbulence channel shows the same performance as SIM with variance of 0.3. This means that the SIM/SM can be an alternative choice in even worse environments.

We characterized bulk-heterojunction (BHJ) solar cells using a new phenylene-thiophene oligomer, 3,7-bis[5-(4-n-hexylphenyl)-2-thienyl]dibenzothiophene-5,5-dioxide (37HPTDBTSO), and phenyl-C61-butyric-acid methyl ester (PCBM). Their photovoltaic properties including current-voltage characteristics and spectrum response were investigated. It was found that 37HPTDBTSO is appraised to be valuable electron donor. The characteristics of BHJ solar cells using mixed two donors of 37HPTDBTSO and a polymer of poly(3-hexylthiophene) (P3HT) were further investigated. OSC using the blend film of mixed donars and PCBM achieved a power conversion efficiency of 0.89%.