Search

We examine the characteristics of a 4-stage nested Mach-Zehnder interferometer optical switch with phase generating couplers, and demonstrate that crosstalk is suppressed to less than -40 dB over 200nm wavelength range from 1450 to 1650 nm by choosing six ports among 16 output ports.

Two-dimensional (2-D) full-tensor anisotropic metamaterials with the impedance of free space are presented based on the theory of the 2-D distributed transmission-line models. A method for determining the structural parameters is shown through a design of a beam shifter based on transformation electromagnetics to translate incident plane waves according to the coordinate system transformed from the original one. In addition, the broadband operations of the beam shifter for electromagnetic waves propagating in free space are numerically demonstrated by full-wave simulations.

A design method for negative refractive index (NRI) metamaterials is proposed based on the transmission-line (TL) approach. A distributed TL model is introduced to the design and the design formulas are shown. A NRI lens operating at 3.85 GHz is designed with the model as an example. The operation and the validity of the design method are exhibited from the calculated results by circuit simulations with a SPICE simulator.

A design method for two-dimensional (2-D) zero-index materials (ZIMs) is presented based on the transmission-line (TL) approach in order to realize invisible cloaks for hiding objects. A simple 2-D distributed TL model is proposed and the formula to calculate the dispersion characteristics is theoretically derived. It is shown from the calculated dispersion characteristics that a Dirac cone is always formed at the T -point without adjustments of the unit cell for the degeneration of propagation modes and ZIMs can be easily designed with the proposed model. In addition, a ZIM operating at 5 GHz is designed with the proposed model, and its cloaking operations and the validity of the design theory are demonstrated by circuit simulations.

We extend the theory of equivalent circuit models for two-dimensional (2-D) full-tensor anisotropic electromagnetic metamaterials and introduce the design method with equivalent circuit models to designs of 2-D full-tensor anisotropic acoustic metamaterials. Relations of circuit parameters and material parameters including the off-diagonal components of the mass density tensor are revealed from the duality of circuit equations and acoustic equations. A 2D acoustic carpet cloak for hiding a bump on a flat surface is designed with equivalent circuit models to confirm the validity of the theory. Circuit simulations are carried out and the voltage distributions and the radar cross sections are compared with those for the cases with the flat surface and the bump. Those results show the angle independent cloaking operations of the designed acoustic carpet cloak.

We demonstrate a $1 \times \mathrm {N}$ nested Mach-Zehnder interferometer optical switch configuration with low crosstalk regardless of coupling ratio deviation. It also has an inherent symmetry which helps a scale expansion of its port count.

We propose a joint-switching architecture utilizing waveguide-based multicast switches in a colorless, directionless and contentionless ROADM node for multi-core fiber networks cost-effectively.

A concept of a flat retroreflector mimicking a cylindrical retroreflector with a function of a Luneburg lens is presented based on the transformation electromagnetics. The retroreflector has retroreflection characteristics even through the mirror surface is flat, and operates with wide incident angles. The retroreflector is designed with equivalent circuit models of full-tensor anisotropic metamaterials. Circuit simulations are carried out with a SPICE simulator in order to confirm the validity of the design and the operations. Simulation results show theoretically the retroreflection operations with wide incident angles and the validity of the concept.

Recently, even a small cube satellite carries a Ku-band transponder and, then, its reception system is required in an earth radio station. A local oscillator (LO) frequency is so high that control and management of the frequency and phase becomes a big issue. We propose optoelectronic frequency conversion using an electro-absorption modulated laser, where LO-on-fiber and IF-on-fiber is transmitted as uplink and downlink, respectively, in a single fiber. The electro-absorption modulator functions as a photodiode to the uplink LO-on-fiber signal as well as the light modulator to convert radio frequency subcarrier in this system.

As a novel application based on the transformation electromagnetics, a flat focusing reflector is presented. This reflector mimics a conventional parabolic reflector, and the reflected waves can be focused at a point even through the mirror surface is flat. By employing equivalent circuit models of the distributed full-tensor anisotropic metamaterials, the flat focusing reflector is designed and its operations are analyzed by circuit simulations.

A flat reflector having retroreflection characteristics is presented based on transformation electromagnetics. The retroreflector is designed with a distributed full-tensor anisotropic metamaterial. Its retroreflection operations are confirmed by circuit simulations based on the equivalent circuit model of the distributed anisotropic metamaterial.

We demonstrate a compact 8 × 8 broadcast-and-select wavelength cross connect with add/drop ports for 8-degree node. A combination of waveguide-based frontend and free-space optics allows us to integrate eight arrays of 1 × 8 WSSs and 1 × 8 splitters into a small footprint.

We introduce an asymmetric-port-count DC switch that can simplify fiber connection arrangement in a large-scale optical switch. A 24×4 DC switch is monolithically implemented with PLC technologies and its good performance is experimentally confirmed.

We propose a method for disaggregating the current waveforms of appliances from a current waveform on a power distribution board. We focus on the case where some appliances have current waveforms that vary continuously and non-proportionally. Our method is a variation of the least squares method with an asymmetric evaluation function. We calculate a standard waveform for each appliance, and we inscribe the standard waveforms to the current waveform on the power distribution board. We apply our method to the aggregate current waveforms of three appliances and compare the results with the least squares method.

We propose a novel tunable-filter configuration for optical C/D/C drop in ROADMs, which achieves low insertion loss and low power consumption. A prototype is monolithically fabricated with PLC technologies and its good filtering performance is experimentally confirmed by BER measurement.

Cost comparison of Colorless and Directionless (CD) or Colorless, Directionless, and Contention-less (CDC) ROADM architectures with different TransPonder Aggregator (TPA) configuration was performed. It is clarified that the most economic TPA-based ROADM architecture depends on network details such as add/drop ratio.

We propose a method for detecting precursors, such as small rock and/or soil fall, which occur prior to massive slope failure. The key feature of our method is directly recognizing the trajectory of a small collapse using spatiotemporal Gabor filtering. Simulation analysis, where the conditions of the simulation are quantitatively defined, reveals the effectiveness of the proposed method in detecting a tiny moving object with low contrast in the background under low frame-rate video monitoring. Experiments using actual monitoring videos of a hazardous slope confirmed the effectiveness of our method. The effects of error factors in an outdoor environment, which may inhibit recognition, are also evaluated.

We propose an improved decentralized method for environment control in wireless sensor/actuator networks. In our method, the objective function is defined to balance energy saving against control signal quality. Each sensor node calculates initial values in an iterative process for estimating optimal control signals using the sensor signals received from neighboring nodes. We evaluated its accuracy and efficiency by using Motes.

The authors have demonstrated an opto-electronic type wavelength switchable converters to apply them to a virtual wavelength path photonic transport system (VWP-PTS). A WP-type-PTS (without wavelength conversion) with 320 Gb/s throughput was demonstrated by pairing an optical receiver (OR) to a fixed wavelength optical sender (OS) instead of wavelength converters.

Single-mode optical waveguides were fabricated by using a newly synthesized polymer, deuterated polysiloxane, which has a high transparency and a high thermal stability. The propagation loss of the waveguides was found to be less than 0.1 dB/cm at 1.31 /spl mu/m and less than 0.5 dB/ cm at 1.55 /spl mu/m. The environmental stability of the waveguides was confirmed by performing tests at different conditions.

A method is proposed for controlling the tactile sensation of surface roughness. This method creates a smoother feeling on a surface by applying ultrasonic vibration, with a few micrometers amplitude, to the surface. The sensation can thus be controlled without altering the actual surface profile. Experiments using five to ten subjects showed the properties of the proposed method, such as the effect of ultrasonic vibration on tactile sensation, the positive relationship between the generation of a smooth feeling and vibration amplitude, and the dependence on vibration frequency. The typical perceived feeling with this method, 'air smoothness', is postulated to be due to the 'squeeze air film effect' between the finger and the surface. The calculated squeeze force qualitatively agreed well with our experimental results. The proposed method also enables the generation of resistant impressions, such as 'the surface is rougher/more sticky' and 'a virtual protrusion exists on the surface', when the duration of the ultrasonic vibration is short enough.