We experimentally evaluated an active speech control scheme which reduces unnecessary speech radiated into the surrounding space. The intended application of this system, typically cellular phones, does not require speech to be radiated into the surrounding space, but only into the microphone. We previously proposed to reduce speech by generating phase-inverted predicted speech from a secondary loudspeaker. We used LPC recursively to predict samples ahead of the associated processing delay, which could go up to a few milliseconds. First, predicted samples of recorded speech were prepared off line. Then, both the original and the phase-inverted predicted samples were played out simultaneously from two loud speakers. It was found that: 1) speech cancellation of 10 dB is possible, but is highly speaker dependent; 2) the secondary loudspeaker should be oriented in the same direction as the primary source, i.e., the mouth for maximum cancellation.

The steady increase in the volume of data transmitted over ATM networks suggest that even a single link failure will seriously impact many service users. Thus, it is very important to develop restoration mechanisms that minimize the impact on the affected services. Self-healing algorithm can be used to automatically restore failed VPs (virtual paths) in backbone ATM networks. In this environment, a major research challenge is to understand the fundamental tradeoff between the capacity of the failed links and importance of the last calls with the reliability level of VPs, and to create a self-healing algorithm for VP capacity allocation that achieves an optimal network operating point. This paper focuses on evaluating the efficiency of the self-healing algorithm, C-TRUS, under the multi-failure scenario for different network topologies and loads and, compares its behavior to that of the combination method. The simulation results show that our approach can build survivable networks with improved reliability that meet different service class requirements.

Challenges of next-generation transmission technologies are summarized in the context of creating future terabit-per-second networks. The technologies will be realized through both the separate and combined evolution of inherent lightwave capabilities along with time-, wavelength-, and space-domain optical processing techniques. Optical signal processing techniques in the tens of gigabit per second range for future high-speed transmission systems and broadband networks are reviewed.>

The authors discuss the design and performance of monolithic ICs for multigigabit lightwave transmission systems including direct detection and coherent detection. The required function and performance of a lightwave transmitter and receiver are discussed. The fabricated ICs and their application to the transmission system are shown in a direct system. Microwave monolithic ICs for lightwave heterodyne detection and an interconnection technique are introduced. Future trends of ICs are discussed.>

A line code called DmB1M that is suitable for a very high-speed, optical, digital-transmission system is described. This code possesses a good balance of marks, spaces, and jitter-suppression capability, as well as a simple in-service error-monitoring function. A fundamental analysis of the DmB1M code is presented, along with experimental results at 1.8 Gb/s. Advantages of this code in parallel signal processing, such as error checking to avoid error propagation, and applications of this code to phase-shift keyed (PSK) systems are also discussed.>

Long-wavelength single-mode optical fiber transmission technology has recently made rapid progress and is now moving into the commercial operation stage. The introduction of high-speed single-mode systems to long-haul trunk transmission systems is quite attractive from the viewpoint of cost effectiveness and network digitalization. This paper describes the system requirements as well as the key technology for the systems with empasis on the transmission characteristics of high-speed single-mode systems.

An evaluation of the influence of mode partition noise on error rate performance in a high bit rate optical fiber transmission system is presented. First, it is experimentally clarified that the intensity in each longitudinal mode of a laser diode fluctuates, although the intensity for the total mode is constant. It is also established that this fluctuation causes degradation of the error rate performance after transmission through a long optical fiber. The fluctuation is named "mode partition noise." Next a simple model for the fluctuation is proposed. The characteristics of the fluctuation are discussed on the basis of this model. Optical waveform fluctuation is found to be introduced by mode partition noise in the course of transmission through a long despersive transmission medium. This optical waveform fluctuation and its frequency spectrum are calculated. Finally, the error rate performance is evaluated and specifications required for a laser spectrum to attain a given repeater spacing are clarified.