We propose an ultra-low inter-core crosstalk (XT) multi-core fiber (MCF) with standard 125-μm cladding. We show the fiber design and fabrication results of an MCF housing four cores with W-shaped index profile; it offers XT of less than -67dB/km over the whole C+L band. This enables us to realize 10,000-km transmission with negligible XT penalty. We also observe a low-loss of 0.17dB/km (average) at a wavelength of 1.55μm and other optical properties compatible with ITU-T G.654.B fiber. We also elucidate its good micro-bend resistance in terms of both the loss and XT to confirm its applicability to high-density optical fiber cables. Finally, we show that the fabricated MCF is feasible along with long-distance transmission by confirming that the XT noise performance corresponds to transmission distances of 10,000km or more.

We investigated the effects of a bending stress on the change in phase retardation of curved polycarbonate substrates and optical characteristics of flexible liquid crystal displays (LCDs). We clarified that the change in phase retardation was extremely small even for the substrates with a small radius of curvature, because bending stresses occurred in the inner and upper surfaces are canceled each other out. We compensated for the phase retardation of polycarbonate substrates by a positive C-plate and successfully suppressed light leakage in both non-curved and curved states. These results indicate the feasibility of high-quality flexible LCDs using polycarbonate substrates even in curved states.

In this paper, we propose a tightly coupled asymmetrically tapered bend to suppress differential-to-common mode conversion caused by bend discontinuity in a pair of differential lines. Tightly coupled symmetrically tapered bends have been so far proposed to suppress the mode conversion by decreasing the path difference in the bend. This approach makes the path difference shorter so that the differential lines are coupled more tightly but the path difference of twice the sum of the line width and the line separation still remains. To suppress the remaining path difference, this paper introduces the use of asymmetric tapers. In addition, two-section tapers are applied to reduce differential-mode reflection increased by the tapers and hence improve differential-mode propagation. A full-wave simulation of a right-angled bend demonstrates that the forward differential-to-common mode conversion is decreased by almost 30 dB compared to the symmetrically tapered bend and that the differential-mode reflection coefficient is reduced to the same amount as that of the classic bend. Also, the generality of the proposed bend structure is discussed.

We realized single-mode hole-assisted optical fiber (HAF) cord whose fiber has a superior bending loss characteristic that complies with ITU-T Recommendation G. 657 for use in highly reliable optical fiber distribution facilities in central offices. The cord has an excellent anti-shock characteristic, and can be scanned by a conventional optical fiber cord identifier despite its very low bending loss. Experiments show that the single-mode HAF cord and its application to optical signal distribution in a central office can provide highly service reliability.

The characteristics of hole-assisted fiber (HAF) are investigated both numerically and experimentally in terms of its applicability as a bending-loss insensitive fiber (BIF). We show that HAF with the desired mode-field diameter (MFD), bending-loss and cutoff wavelength characteristics can be roughly designed by taking a few specific structural parameters into consideration. We also show that an optical cord composed of adequately designed HAF realizes satisfactory transmission performance with respect to its multi-path interference (MPI) characteristics. These results reveal that a hole-assisted type BIF will be beneficial for realizing easy and economical installation and maintenance in future access networks.

In this paper, the transmission and reflection properties of the microstrip line with bends are investigated using the Fourier transform and a mode-matching technique. Based on the waveguide model, the microstrip bends are modeled as the rectangular waveguides with perfect electric conducting top and bottom walls and perfect magnetic conducting side walls. Analytical closed-form expressions for transmission and reflection coefficients are developed using the residue calculus. To verify the proposed method, numerical computations are performed for comparison with 3D full-wave simulations and measurements. A quarter-wavelength transmission line scheme is also proposed to improve the signal integrity of double bend discontinuity.

In equational theorem proving, convergent term rewriting systems play a crucial role. In order to compute convergent term rewriting systems, the standard completion procedure (KB) was proposed by Knuth and Bendix and has been improved in various ways. The multi-completion system MKB developed by Kurihara and Kondo accepts as input a set of reduction orders in addition to equations and efficiently simulates parallel processes each of which executes the KB procedure with one of the given orderings. Wehrman and Stump also developed a new variant of completion procedure, constraint-based completion, in which reduction orders need not be given by using automated modern termination checkers. As a result, the constraint-based procedures simulate the execution of parallel KB processes in a sequential way, but naive search algorithms sometimes cause serious inefficiency when the number of the potential reduction orders is large. In this paper, we present a new procedure, called a constraint-based multi-completion procedure MKBcs, by augmenting the constraint-based completion with the framework of the multi-completion for suppressing the combinatorial explosion by sharing inferences among the processes. The existing constraint-based system SLOTHROP, which basically employs the best-first search, is more efficient when its built-in heuristics for process selection are appropriate, but when they are not, our system is more efficient. Therefore, both systems have their role to play.

Gas or water leaks in pipes that are buried under ground or that are situated in the walls of buildings may occur due to aging or unpredictable accidents, such as earthquakes. Therefore, the detection of leaks in pipes is an important task and has been investigated extensively. In the present paper, we propose a novel leak detection method by means of acoustic wave. We inject an acoustic chirp signal into a target pipeline and then estimate the leak location from the delay time of the compressed pulse by passing the reflected signal through a correlator. In order to distinguish a leak reflection in a complicated pipeline arrangement, the reflection characteristics of leaks are carefully discussed by numerical simulations and experiments. There is a remarkable difference in the reflection characteristics between the leak and other types of discontinuity, and the property can be utilized to distinguish the leak reflection. The experimental results show that, even in a complicated pipe arrangement including bends and branches, the proposed approach can successfully implement the leak detection. Furthermore, the proposed approach has low cost and is easy to implement because only a personal computer and some commonly equipment are required.

The dispersion and the splice characteristics of optical fibers with trench-index profile are investigated. The normalized distance between core and trench is preferably larger than 3.0 to realize complete compatibility with the standard G.652 fiber in terms of chromatic dispersion. The optical fiber realizes compatibility with ITU-T Recommendation G.652 fiber and bend-insensitivity simultaneously. Fabricated fibers with the trench-index profiles can be spliced to standard single-mode fiber with low losses, which have similar values with simulation results.

A metallic waveguide with dual in-line dielectric rods can propagate electromagnetic waves more than two times higher than the cutoff frequency region and without higher modes [1]. If the straight portion in the waveguide has even symmetry, then dielectric rods are only required in the bent portion. Connection losses between the portions are improved by adding other dielectric rods.

The crosstalk phenomenon, wich occurs between transmission lines, is caused by electromagnetic fields of currents flowing through the lines. Crosstalk between two bent lines is studied by using a set of solutions of modified telegrapher's equations. By expressing electromagnetic fields in terms of voltages and currents in the line ends, the resultant network function in the form of an ABCD matrix is obtained. Electromagnetic fields caused by currents flowing in risers at transmission line ends are taken into account in addition to those fields in line sections. The validity of the proposed approach was confirmed by comparing experimental results with computed results and those simulated by a commercial electromagnetic solver for some bent-line models.

A micromirror for an external cavity diode laser is described. The mirror is supported by two sets of parallel torsion bars enabling piston motion as well as rotation. These motions are for realizing continuous wavelength tuning. Adjusting two rotations electrically, the pivot of the mirror rotation can be controlled. The long stroke of the vertical comb is realized by the deep three-dimensional structure prepared by the wafer bending method.

An electrostatically driven micromirror is described. The vertical comb of a three-dimensional microstructure is realized by bending the device wafer having microstructures. By resetting the bending angle, the tuning of the vertical gap between moving and stationary combs is possible. The characteristics of the vertical comb drive actuator can be tuned, confirming the performance.

We have developed a novel type of holey fiber which has a conventional raised-index core surrounded by two layers of air holes with different sizes. The fiber has single-mode operation and shows a low bending loss even for an extremely small bending diameter and a low splicing loss for fusion splicing to a conventional single-mode fiber. The structure and the properties of the fiber are reported in this paper.

Discontinuity such as a bend in a micro-strip line is known as one of major radiation sources. The total radiation from the micro-strip line is, however, being generally investigated because of the difficulties in identifying the radiation from some specific location. In this paper, paying attention to the feature of TDR (Time-Domain Reflectometry) measurement, we made an attempt to extract the radiation only from the bend in a micro-strip line. Such an approach is useful in understanding its radiation mechanism. As a result, we found that the larger the bend angle is, the larger the radiation power becomes. The radiation power achieved 3.5% at maximum when the bending angle was 90at the frequencies below 1 GHz. We also examined the validity of the TDR analysis in comparison with network analyzer measurement. We obtained the radiation power versus frequency from the measured scattering parameters, which exhibited a fair agreement with the TDR result.

In this paper we show that an outerplanar graph G with maximum degree at most 3 has a 2-D orthogonal drawing with no bends if and only if G contains no triangles. We also show that an outerplanar graph G with maximum degree at most 6 has a 3-D orthogonal drawing with no bends if and only if G contains no triangles.

A single-mode fiber employing a trench index profile for indoor wiring is proposed to realize low-bending loss and low-splice loss simultaneously. The designs and the advantages of the fiber over fibers with conventional step index profiles are described. The characteristics of manufactured fibers with trench index profiles are also described. One of the manufactured fibers realizes a bending loss of 0.018 dB/turn at 1550 nm for a bending radius of 7.5 mm, and a splice loss of 0.19 dB at 1550 nm in mechanical splicing to a conventional single mode fiber simultaneously. Other one of the fibers realizes a bending loss of 0.011 dB/turn at 1550 nm for a bending radius of 5 mm, and the splice loss is 0.37 dB at 1550 nm simultaneously. A total loss of a fiber employing the trench index is small and stable against the fluctuation of MFD.

This paper reports on the bending loss insensitive single mode fiber suitable for access networks, which is applicable for wide wavelength use. Excellent attenuation stability of the fiber in the full spectrum range has been confirmed even in severe conditions such as fiber handling in mid-span access at aerial closure, cable installation/handling in indoor wirings and so on. Also, applications suitable for FTTH subscribers' use have been introduced.

A plane graph is a planar graph with a fixed embedding. In a no-bend orthogonal drawing of a plane graph, each vertex is drawn as a point and each edge is drawn as a single horizontal or vertical line segment. A planar graph is said to have a no-bend orthogonal drawing if at least one of its plane embeddings has a no-bend orthogonal drawing. In this paper we consider a class of planar graphs, called subdivisions of planar triconnected cubic graphs, and give a linear-time algorithm to examine whether such a planar graph G has a no-bend orthogonal drawing and to find one if G has.

Recent new technologies of electro-mechanical conversion devices have been reviewed. Especially, the electrochemical properties of anisotropic actuators using polypyrrole have been reviewed in detailed and the realization of the bimorph (or bending beam) structure without artificial adhesive agent is introduced.