This paper proposes a fault tolerant optical crossconnect (FTOXC) which can tolerate link, channel, and internal optical switch failures via spare optical channels, extra input/output (I/O) ports for an optical switch, and associated wavelength converters. It also proposes a fault tolerant wavelength routing algorithm (FTWRA) which is used in the normal and the restored state. The FTOXC and FTWRA can be applied to any all-optical network and can recover many types of failures. FTOXC can configure the number of working and spare channels in each output link based on the traffic demand. Two formulations in this paper can be used to determine the optimal settings of channels. A global optimal setting of working and spare channels in each link can be found by formulating the problem as an integer linear program (ILP). In addition, the number of working and spare channels in each link can be dynamically adjusted according to the traffic loads and the system reliability requirements. The tradeoff between these two conflicting objectives is analyzed by the Markov decision process (MDP).

This paper describes an all-optical label swapping for the photonic label switching router (LSR). The optical code routing photonic LSR in which label is mapped onto an optical code is one of the most promising photonic network technologies. It utilizes such unique features of optical code division multiplexing (OCDM) as asynchronous transmission, tell-and-go access protocol, and high degree of scalability. In practical photonic LSRs, all optical code conversion will play an important role. All-optical code conversion of 10 Gbit/s binary phase-shift keying (BPSK) codes by use of cross-phase modulation (XPM) in an optical fiber without wavelength-shift is proposed for the photonic LSR and experimentally demonstrated.

In this article, we first discuss QoS metrics of the data networks, followed by raising the challenging problems for the next-generation Internet with high-performance and high-quality. We then discuss how the WDM technology can be incorporated for resolving those problems. Several research issues for the IP over WDM networks are also identified.

An optical spectral coding scheme is devised for fiber-optic code-division multiple-access (FO-CDMA) networks. The spectral coding is based on the pseudo-orthogonality of FO-CDMA codes properly written in the fiber Bragg grating (FBG) devices. For an incoming broadband optical signal having spectral components equal to the designed Bragg wavelengths of the FBG, the spectral components will be reflected and spectrally coded with the written FO-CDMA address codes. Each spectral chip has different central wavelength and is distributed over the spectrum of the incoming light source. Maximal-length sequence codes (m-sequence codes) are chosen as the signature or address codes to exemplify the coding and correlation processes in the FO-CDMA system. By assigning the N cycle shifts of a single m-sequence code to N users, we get an FO-CDMA network that can theoretically support N simultaneous users. To overcome the limiting factor of multiple-access interference (MAI) on the performance of the FO-CDMA network, an FBG decoder is configured on the basis of orthogonal correlation functions of the adopted pseudo-orthogonal codes. An intended receiver user that operates on the defined orthogonal correlation functions will reject any interfering user and obtain quasi-orthogonality between the FO-CDMA users in the network. Practical limiting issues on networking performance, such as non-flattened source spectra, optical path delay, and asynchronous data accesses, are evaluated in terms of the bit-error-rate versus the number of active users. As expected, the bit-error-rate will increase with the number of active users. Increasing the flatness parameter of optical signal will lead to a lower average error probability, since we are working in a part of the more flattened optical spectrum. In contrast, reducing the encoded bandwidth will reduce the total received power, and this will necessitate higher resolution of fiber Bragg gratings.

In this paper, two distinct optical network design approaches, namely mesh and multi-ring, for survivable WDM networks are investigated. The main objective is to compare these two design approaches in terms of network costs so that their merits in practical environments can be identified. In the mesh network design, a new mathematical model based on integer liner programming (ILP) and a heuristic algorithm are presented for achieving a minimal cost network design. In the multi-ring network design, a heuristic algorithm that can be applied to large network problems is proposed. The influence of wavelength conversion and the number of wavelengths multiplexed in a fiber on system designs are also discussed. Based on the simulation results, the redundancy quantities required for full protection in multi-ring approach are significantly larger in comparison to the minimal cost mesh counterpart.

High-capacity multiwavelength ring networks with bidirectional WDM add/drop multiplexer (WADM) having built-in EDFAs is analyzed and demonstrated. All WDM channels can be added/dropped independently in each direction. The capacity of a bidirectional ring is found to be approximately twice that of an unidirectional ring. An eight-wavelength WADM is demonstrated for a data rate of 10 Gb/s per channel, providing an overall capacity of 80 Gb/s. The performance of the add/drop multiplexer is not degraded by backward backscattering light. The same WADM is also demonstrated to be able to serve as a bidirectional in-line optical amplifier.

In this paper the novel method of "weighted OFDM" is addressed. Different types of weighting factors (including Rectangular, Bartlett, Gaussian, Raised cosine, Half-sin and Shanon) are considered. The impact of weighting of OFDM on the peak-to-average power ratio (PAPR) is investigated by means of simulation and is compared for the above mentioned weighting factors. Results show that by weighting of the OFDM signal the PAPR reduces. Bit error performance of weighted multicarrier transmission over a multipath channel is also investigated. Results indicate that there is a trade off between PAPR reduction and bit error performance degradation by weighting.

A high speed 3D shape reconstruction method with multiple video cameras and multiple computers on LAN is presented. The video cameras are set to surround the real 3D space where people exist. Reconstructed 3D space is displayed in voxel format and users can see the space from any viewpoint with a VR viewer. We implemented a prototype system that can work out the 3D reconstruction with the speed of 10.55 fps in 313 ms delay.

We present a new basis for discrete representation of stereo correspondence. This center referenced basis permits a more natural, complete and concise representation of constraints in stereo matching. In this context a MAP formulation for disparity estimation is derived and reduced to unconstrained minimization of an energy function. Incorporating natural constraints, the problem is simplified to the shortest path problem in a sparsely connected trellis structure which is performed by an efficient dynamic programing algorithm. The computational complexity is the same as the best of other dynamic programming methods, but a very high degree of concurrency is possible in the algorithm making it suitable for implementation with parallel procesors. Experimental results confirm the performance of this method and matching errors are found to degrade gracefully in exponential form with respect to noise.

In industrial assembly lines, seam sealing is a painting process used for making watertight seals or for preventing rusting. In the process, sealant is painted on seams located at the joints of pressed metal parts. We developed a sealing robot system that adjusts the sealing gun motion adaptively to the seam position sensed by a range sensor (a scanning laser rangefinder which senses profile range data). In this paper, we propose a high-speed and highly reliable algorithm for seam position computation from the sensed profile range data around the seam. It is proved experimentally that the sealing robot system used with the developed algorithm is very effective, especially for reducing wasted sealant.

Wavelength-division multiplexing (WDM) technique employing broadband erbium-doped fiber amplifiers (EDFAs) is considered to be the most effective solution to respond to the increasing demand for transmission capacity. As a means to extend the optical bandwidth outside the conventional band (C-band) ranging from 1530 to 1565 nm, silica-based EDFAs (EDSFAs) operating within the long-wavelength band (L-band) ranging form 1570 to 1600 nm seem to be the most attractive candidate because they can be composed of the same material as C-band EDSFAs, i. e. silica-based Al codoped EDF. However, there exist several discrepancies between C-band and L-band EDSFAs which originate inevitably from the difference in the inversion level and the band location. This paper reviews the basic characteristics of L-band EDSFAs, which have been a controversial issue for practical application of the L-band EDSFAs, such as required EDSF lengths, power conversion efficiency, noise performances, and optical bandwidth. We will also describe L-band EDSFAs' behavior under circumstantial changes, such as the variation of the span-loss, the temperature of the EDSF, and the number of wavelengths, which are expected in the field WDM systems. The dynamic-gain-tilt and temperature-induced change in the gain spectra of L-band EDSFAs are more significant than those of C-band EDSFAs are. Moreover, L-band EDSFAs exhibit a greater apparent inhomogeneous broadening effect, which may hinder the precise gain control when the number of wavelengths is dynamically changed. All of these characteristics must be considered for future designs of broadband WDM networks.

We propose a new active vision system that mimics a saccadic movement of human eye. It is implemented based on a new computational model using neural networks. In this model, the visual pathway was divided in order to categorize a saccadic eye movement into three parts, each of which was then individually modeled using different neural networks to reflect a principal functionality of brain structures related with the saccadic eye movement in our brain. Initially, the visual cortex for saccadic eye movements was modeled using a self-organizing feature map, then a modified learning vector quantization network was applied to imitate the activity of the superior colliculus relative to a visual stimulus. In addition, a multilayer recurrent neural network, which is learned by an evolutionary computation algorithm, was used to model the visual pathway from the superior colliculus to the oculomotor neurons. Results from a computer simulation show that the proposed computational model is effective in mimicking the human eye movements during a saccade. Based on the proposed model, an active vision system using a CCD type camera and motor system was developed and demonstrated with experimental results.

A new computational method for evaluating the reverse-link interference distribution in a cellular CDMA system is proposed. In particular, a positive feedback effect of the reverse-link closed-loop power control has been taken into account to precisely capture a realistic effect of unequal cell loading on system capacity. It subsequently facilitates computing the frequency reuse efficiency of the cellular CDMA system under unequal cell loading.

More than forty thousands computer viruses have appeared so far since the first virus. Six computer viruses on average appear every day. Enormous expansion of the computer network opened a thread of explosive spread of computer viruses. In this paper, we propose a distributed approach against computer virus using the computer network that allows distributed and agent-based approach. Our system is composed of an immunity-based system similar to the biological immune system and recovery system similar to the recovery mechanism by cell division. The immunity-based system recognizes "non-self" (which includes computer viruses) using the "self" information. The immunity-based system uses agents similar to an antibody, a natural killer cell and a helper T-cell. The recover system uses a copy agent which sends an uninfected copy to infected computer on LAN, or receives from uninfected computer on LAN. We implemented a prototype with JAVATM known as a multi-platform language. In experiments, we confirmed that the proposed system works against some of existing computer viruses that can infect programs for MS-DOSTM.

The sense of equilibrium is influenced by various factors of visual stimulation, especially far peripheral vision and a motion parallax. An investigation of these two factors was made in order to apply the findings to construct a rehabilitation method for equilibrium disorders. From the experimental results, it was found that the center of gravity for the subjects was greatly affected by both far peripheral vision and the motion parallax. This finding suggests how visual stimulation should be displayed to control the sense of balance in the case of equilibrium disorders.

Characteristics of an FBG hydrophone are described under various conditions. The developed FBG hydrophone detects an acoustic field in water with good performances: linear response,high sensitivity,high stability,wide dynamic range as large as 90 dB and wide operation frequency range from a few kHz to a few MHz. A WDM FBG hydrophone consisting of two FBGs in serial connection can detect simultaneously amplitudes and phases of acoustic fields at different points,which in turn allows a directive measurement of an acoustic field in water.

The wavelength demultiplexer, using cascaded optical fiber gratings and circulators, was proposed and developed for application to optically amplified wavelength-division multiplexing (WDM) submarine cable systems with 100 GHz channel spacing. Our proposed demultiplexer cannot only achieve high wavelength selectivity, small excess loss and effective allocation of dispersion compensation fibers for each channel, but also be upgraded without affecting other existing channels. By using this demultiplexer, it has been successfully confirmed that 8 WDM channels were demultiplexed even after 6,000 km transmission including separate compensation of accumulated chromatic dispersion in each channel.

For measuring high frequency ultrasonic fields which are often spatially distributed and transient, an array probe with small element sensors is highly required. In this paper, we propose a fiber-optic micro-probe array which is based on wavelength-division-multiplexing technique. The element sensor consists of a micro optical cavity of 100 µm long made at the end of optical fiber. Optical path length of the cavity is changed by the applied acoustic field, and the modulation of output light intensity is monitored at another end of the fiber for the information of the acoustic field. Array of sensor elements and a light source as well as a photo detector are connected together by an optical star coupler. The Fabry-Perot resonance wavelength of each sensor element is designed different one another, and the outputs from the sensors are discriminated by sweeping the wavelength of light source with the use of a tunable semiconductor laser. In this paper, the performance of the micro-probe array is discussed experimentally.

This paper describes a nonblind digital beamformer for SDMA (space division multiple access) systems used when channels are power-limited. An array antenna with many elements is usually required to obtain high antenna gain for the reception of a low-level desired signal and the degree of freedom for the spatial discrimination of many users using the same frequency. The proposed beamformer is designed for such array antennas by employing the combination of a multibeam former and a maximal-ratio-combining (MRC) technique. The MRC technique is extended to a nonblind combiner that uses a training sequence contained in the desired signal. Basic analysis and numerical simulations of its performance, under the power-limited condition and with fixed user terminals, show that the speed and robustness of desired-signal acquisition and undesired-signal suppression may outperform recursive-least-squares (RLS) beamformer with less computation, when it is applied to an array antenna with many elements.

A data-parallel processing approach is promising for real-time volume rendering because of the massive parallelism in volume rendering. In data-parallel volume rendering, local results processing elements(PEs) generate from allocated subvolumes are integrated to form a final image. Generally, the integration causes an overhead unavoidable in data-parallel volume rendering due to communications among PEs. This paper proposes a data-parallel shear-warp volume rendering algorithm combined with an adaptive volume subdivision method to reduce the communication overhead and improve processing efficiency. We implement the parallel algorithm on a message-passing multiprocessor system for performance evaluation. The experimental results show that the adaptive volume subdivision method can reduce the overhead and achieve higher efficiency compared with a conventional slab subdivision method.