A novel resilient coarse granularity optical routing network architecture that adopts finely granular protection and finely granular add/drop is presented. The routing scheme defines optical pipes such that multiple optical paths can be carried by each pipe and can be dropped or added at any node on the route of a pipe. The routing scheme also makes it possible to enhance frequency utilization within pipes, by denser path packing in the frequency domain, as we recently verified. We develop a static network design algorithm that simultaneously realizes the independence of working and backup paths and pipe location optimization to efficiently carry these paths. The design algorithm first sequentially accommodates optical paths into the network, then tries to eliminate sparsely utilized fibers and iteratively optimizes frequency slot/wavelength assignment in each coarse granular pipe so as to limit the impairment caused by dropping the optical paths adjacent in the frequency domain. Numerical experiments elucidate that the number of fibers in a network can be reduced by up to 20% for 400Gbps channels without any modification in hardware.

Recently we proposed a new waveband MUX/DEMUX that uses two concatenated cyclic AWGs. We analyse and formulate connection arrangements of the waveguides connecting the two AWGs. The port utilization of the device is shown to be 100% with bi-directional input fibers.

To accelerate research on Beyond 5G (B5G) technologies in Japan, we propose an algorithm that designs mesh-type metropolitan area network (MAN) models based on a priori Japanese regional railway information, because ground-truth communication network information is unavailable. Instead, we use the information of regional railways, which is expected to express the necessary geometric structure of our metropolitan cities while remaining strongly correlated with their population densities and demographic variations. We provide an additional compression algorithm for use in reducing a small-scale network model from the original MAN model designed using the proposed algorithm. Two Tokyo MAN models are created, and we provide day and night variants for each while highlighting the number of passengers alighting/boarding at each station and the respective population densities. The validity of the proposed algorithm is verified through comparisons with the Japan Photonic Network model and another model designed using the communication network information, which is not ground-truth. Comparison results show that our proposed algorithm is effective for designing MAN models and that our result provides a valid Tokyo MAN model.

In this paper, we propose a heuristic planning method to efficiently accommodate dynamic multilayer path (MLP) demand in multilayer networks consisting of a Time Division Multiplexing (TDM) layer and a Wavelength Division Multiplexing (WDM) layer; the goal is to achieve the flexible accommodation of increasing capacity and diversifying path demands. In addition to the grooming of links at the TDM layer and the route and frequency slots for the elastic optical path to be established, MLP requires the selection of an appropriate operational mode, consisting of a combination of modulation formats and symbol rates supported by digital coherent transceivers. Our proposed MLP planning method defines a planning policy for each of these parameters and embeds the values calculated by combining these policies in an auxiliary graph, which allows the planning parameters to be calculated for MLP demand requirements in a single step. Simulations reveal that the choice of operational mode significantly reduces the blocking probability and demonstrate that the edge weights in the auxiliary graph allow MLP planning with characteristics tailored to MLP demand and network requirements. Furthermore, we quantitatively evaluate the impact of each planning policy on the MLP planning results.

The novel optical path routing architecture named flexible waveband routing networks is reviewed in this paper. The nodes adopt a two-stage path routing scheme where wavelength selective switches (WSSs) bundle optical paths and form a small number of path groups and then optical switches without wavelength selectivity route these groups to desired outputs. Substantial hardware scale reduction can be achieved as the scheme enables us to use small scale WSSs, and even more, share a WSS by multiple input cores/fibers through the use of spatially-joint-switching. Furthermore, path groups distributed over multiple bands can be switched by these optical switches and thus the adaptation to multi-band transmission is straightforward. Network-wide numerical simulations and transmission experiments that assume multi-band transmission demonstrate the validity of flexible waveband routing.

We propose a demodulation framework to extend the maximum distance of unrepeated transmission systems, where the simplest back propagation (BP), polarization and phase recovery, data arrangement for machine learning (ML), and symbol decision based on ML are rationally combined. The deterministic waveform distortion caused by fiber nonlinearity and chromatic dispersion is partially eliminated by BP whose calculation cost is minimized by adopting the single-step Fourier method in a pre-processing step. The non-deterministic waveform distortion, i.e., polarization and phase fluctuations, can be eliminated in a precise manner. Finally, the optimized ML model conducts the symbol decision under the influence of residual deterministic waveform distortion that cannot be cancelled by the simplest BP. Extensive numerical simulations confirm that a DP-16QAM signal can be transmitted over 240km of a standard single-mode fiber without optical repeaters. The maximum transmission distance is extended by 25km.

We propose an efficient network upgrade and expansion method that can make the most of the next generation channel resources to accommodate further increases in traffic. Semi-flexible grid configuration and two cost metrics are introduced to establish a regularity in frequency assignment and minimize disturbance in the upgrade process; both reduce the fragmentation in frequency assignment and the number of fibers necessary. Various investigations of different configurations elucidate that the number of fibers necessary is reduced about 10-15% for any combination of upgrade scenario, channel frequency bandwidth, and topology adopted.

This paper investigates the prospects and challenges of hierarchical optical path networks. The merits and issues of introducing higher order optical paths are elucidated. State of the art of the key enabling technologies are demonstrated including hierarchical optical cross-connect switch architectures, hierarchical optical path network design algorithms, a newly developed waveband filter, and waveband conversion technologies.

Link-level and node-level blocking in photonic networks has been intensively investigated for several decades and the C/D/C approach to OXCs/ROADMs is often emphasized. However, this understanding will have to change in the future large traffic environment. We herein elucidate that exploiting node-level blocking can yield cost-effective large-capacity wavelength routing networks in the near future. We analyze the impact of link-level and node-level blocking in terms of traffic demand and assess the fiber utilization and the amount of hardware needed to develop OXCs/ROADMs, where the necessary number of link fibers and that of WSSs are used as metrics. We clarify that the careful introduction of node-level blocking is the more effective direction in creating future cost effective networks; compared to C/D/C OXCs/ROADMs, it offers a more than 70% reduction in the number of WSSs while the fiber increment is less than ~2%.

A 1.5 V 8 mW BiCMOS video A/D converter has been developed by using a BiCMOS pumping comparator. Combining Bipolar high-speed and good-matching characteristics with CMOS switched capacitor techniques, this A/D converter is suitable for use in battery-operated multimedia terminals.

In this paper, we propose a projection based design of near perfect reconstruction QMF banks. An advantage of this method is that additional design specifications are easily implemented by defining new convex sets. To apply convex projection technique, the main difficulty is how to approximate the design specifications by some closed convex sets. In this paper, introducing a notion of Magnitude Product Space where a pair of magnitude responses of analysis filters is expressed as a point, we approximate design requirements of QMF banks by multiple closed convex sets in this space. The proposed method iteratively applies a convex projection technique, Hybrid Steepest Descent Method, to find a point corresponding to the optimal analysis filters at each stage, where the closed convex sets are dynamically improved. Design examples show that the proposed design method leads to significant improvement over conventional design methods.

HRTFs (head-related transfer functions) are available for sound field reproduction with spatial fidelity, since HRTFs involve the acoustic cues such as interaural time difference, interaural intensity difference and spectral cues that are used for the perception of the location of a sound image. Generally, FIR filters are used in the simulation of HRTFs. However, this method is not useful for a simply system, since the orders of the FIR filters are high. In this paper, we propose a method using IIR filter for simply realization of sound image localization. The HRTFs of a dummy-head were approximated by the following filters: (A) fourth to seventh-order IIR filters and (B) third-order IIR filters. In total, the HRTFs of 24 different directions on the horizontal plane were used as the target characteristics. Sound localization experiments for the direction and the elevation angle of a sound image were carried out for 3 subjects in a soundproof chamber. The binaural signal sounds using the HRTFs simulated by FIR filters and approximated by IIR filters (A) and (B) were reproduced via two loudspeakers, and sound image localization on the horizontal plane was realized. As the result of the experiments, the sound image localization using the HRTFs approximated by IIR filters (A) is the same accuracy as the case of using the FIR filters. This result shows that it is possible to create sound fields with binaural reproduction more simply.

In this paper, we present a novel iterative MPEG super-resolution method based on an embedded constraint version of Adaptive projected subgradient method [Yamada & Ogura 2003]. We propose an efficient operator that approximates convex projection onto a set characterizing framewise quantization, whereas a conventional method can only handle a convex projection defined for each DCT coefficient of a frame. By using the operator, the proposed method generates a sequence that efficiently approaches to a solution of super-resolution problem defined in terms of quantization error of MPEG compression.

This paper presents a fast and large-scale optical circuit-switch architecture for intra-datacenter applications that uses a combination of space switches and wavelength-routing switches are utilized. A 1,440 × 1,440 optical switch is designed with a fast-tunable laser, 8×8 delivery-and-coupling switch, and a 180×180 wavelength-routing switch. We test the bit-error-ratio characteristics of all ports of the wavelength-routing switch using 180-wavelength 10-Gbps signals in the full C-band. The worst switching time, 498 microseconds, is confirmed and all bit-error ratios are acceptable.

We propose an efficient network design algorithm that realizes shared protection. The algorithm iteratively improves the degree of wavelength resource usage and fiber utilization. To achieve this, we newly define two metrics to evaluate the degree of wavelength resource usage of a pair of working/backup paths and the fiber utilization efficiency. The proposed method iteratively redesigns groups of paths that are selected in the order determined by the metrics. A numerical analysis verifies that the proposed algorithm can substantially reduce the required wavelength resources and hence fiber cost. It is also verified that the computational complexity of the proposed algorithm is small enough to terminate within practicable time.

Adaptive and flexible network control technology is considered essential for efficient network resource utilization. Moreover, such technology is becoming a key to cost-effectively meet diverse service requirements and accommodate heavier traffic with limited network resources; demands that conventional static operation cannot satisfy. To address this issue, we previously studied dynamic network control technology for large-capacity network services including on-demand broad bandwidth provisioning services and layer-one VPN. Our previous study introduced a simple weighting function for achieving fairness in terms of path length and proposed two dynamic Make Before Break Routing algorithms for reducing blocking probability. These algorithms enhance network utilization by rerouting existing paths to alternative routes while completely avoiding disruption for highly reliable services. However, the impact of this avoidance of service disruption on blocking probability has not been clarified. In this paper, we propose modified versions of the algorithms that enhance network utilization while slightly increasing disruption by rerouting, which enable us to elucidate the effectiveness of hitless rerouting. We also provide extensive evaluations including a comparison of original and modified algorithms. Numerical examples demonstrate that they achieve not only a high degree of fairness but also low service blocking probability. Hitless rerouting is achieved with a small increase in blocking probability.

We realize a multicore erbium-doped fiber amplifier (MC-EDFA) with 2dB optical gain improvement (average) by recycling the residual 0.98μm pump light from the MC-EDF output. Eight-channel per core wavelength division multiplexed (WDM) Nyquist PM-16QAM optical signal amplification is demonstrated over a 40-minute period. Furthermore, we demonstrate the proposed MC-EDFA's stability by using it to amplify a Nyquist PM-16QAM signal and evaluating the resulting Q-factor variation. We found that our scheme contributes to reducing the total power consumption of MC-EDFAs in spatial division multiplexing (SDM)/WDM networks by up to 33.5%.

Recently, a great deal of effort has been devoted to the design problem of "constrained least squares M-D FIR filter" because a significant improvement of the squared error is expected by a slight relaxation of the minimax error condition. Unfortunately, no design method has been reported, which has some theoretical guarantee of the convergence to the optimal solution. In this paper, we propose a class of novel design methods of "constrained least squares M-D FIR filter. " The most remarkable feature is that all of the proposed methods have theoretical guarantees of convergences to the unique optimal solution under any consistent set of prescribed maximal error conditions. The proposed methods are based on "convex projection techniques" that computes the metric projection onto the intersection of multiple closed convex sets in real Hilbert space. Moreover, some of the proposed methods can still be applied even for the problem with any inconsistent set of maximal error conditions. These lead to the unique optimal solution over the set of all filters that attain the least sum of squared distances to all constraint sets.

In this paper, the effects of visual information on associated auditory information were investigated when presented simultaneously under dynamic conditions on a wide screen. Experiments of an auditory-visual stimulus presentation using a computer graphics movie of a moving patrol car and its siren sound, which were combined in various locations, were performed in 19 subjects. The experimental results showed the following: the visual stimulus at the beginning of the presentation captured the sound image stronger than that at the end (i.e., beginning effect), the sound image separated from the visual image even when both stimulus locations were exactly at the same place and then when both stimuli moved in opposite directions from each other, the visual stimulus tended to capture the sound image stronger in the peripheral visual field than in the central visual field, and the visual stimulus moving toward the sound source captured the sound image stronger than that moving away from the sound source.

This study compares the performances of waveband protection and wavelength path protection in survivable hierarchical optical path networks. Network costs and the number of switching operations necessary are evaluated for different ratios of protected demand. Numerical results demonstrate that waveband protection can drastically decrease the number of switching operations in the case of failure, while both waveband and wavelength path protection effectively reduce the network resources needed compared to single layer optical path networks.