An optical-transmission error-rate experiment is described in which a single-mode fibre up to 5.9 km long is used as a transmission medium. It is shown that impairments of the transmission was mainly determined by material dispersion and wave-guide-delay distorsion of the transmission medium.

Experimental results of atmospheric light transmission tests for three years, from March 1970 to March 1973, are described. The experiments were performed in the downtown area of Tokyo. A He-Ne laser at the wavelength of 0.63 µm and a light emitting diode at the wavelength of 0.85 µm were used as light sources, which were modulated by PCM signals at a bit rate of 122 Mb/s and 6.3 Mb/s, respectively. It is confirmed that the cumulative probability distribution of lightwave attenuation can be estimated precisely by that of the visual range. Based on the estimation, it will be necessary to use a tandem optical transmission system through the atmosphere with repeaters at intervals shorter than 1 km, in order to attain a higher reliability of about 99.9 percent. In addition, this paper clarifies the dependency of optical pulse atmospheric transmission upon weather conditions under the condition of constant received light power.

In this paper, we propose an extension to GridFTP that optimizes its performance by dynamically adjusting the number of parallel TCP connections. GridFTP has been used as a data transfer protocol to effectively transfer a large volume of data in Grid computing. GridFTP supports a feature called parallel data transfer that improves throughput by establishing multiple TCP connections in parallel. However, for achieving high GridFTP throughput, the number of TCP connections should be optimized based on the network status. In this paper, we propose an automatic parallelism tuning mechanism called GridFTP-APT (GridFTP with Automatic Parallelism Tuning) that adjusts the number of parallel TCP connections according to information available to the Grid middleware. Through simulations, we demonstrate that GridFTP-APT significantly improves the performance of GridFTP in various network environments.

Described here is an automatic text summarization system for Japanese newspaper articles on sassho-jiken (murders and bodily harms). We extract the pieces of information from a text, inter-connect them to represent the scenes and participants involved in the sassho-jiken, and finally produce a summary by generating sentences from the information extracted. An experiment and its evaluation show that, while a limitation being imposed on the domain, our method works well in depicting important information from the newspaper articles and the summaries produced are better in adequacy and readability than those obtained by extracting sentences.

A 400 Mb/s optical fiber fransmission system was designed for field trial using single-mode fibers. The system is targeted to 20 km repeater spacing using InGaAsP/InP DH laser diode (LD) and Ge-APD as an optical device. This paper describes the design philosophy for the single-mode fiber transmission system and the field trial results. The error rate performance is expressed by signal to noise ratio (SNR) for practical high-speed digital optical repeater, putting emphasis on LD mode partition noise. Based on the SNR analysis and results obtained from several preliminary experiments, the design procedures for the 400 Mb/s transmission system were clarified. Through the field trial, it has become clear that the 400 Mb/s optical transmission system is practically applicable to long-haul transmission systems.

This paper is concerned with an experimental approach to determining the feasibility of an optical PCM system at high bit rates. One necessary development is a high speed modulation technique using a semiconductor injection laser. The other is a high sensitivity receiving technique. First, this paper shows that high speed modulation with less pattern effect and less extinction ratio degradation can be effectively performed by adding the undershoot and overshoot to the driving current pulse in an injection laser. Second, this paper shows that a current feedback amplifier, consisting of an emitter-grounded bipolar transistor, is advantageous in high sensitivity of a high speed optical PCM receiving circuit, and to increase in repeater spacing. Finally, it is shown experimentally that the repeater spacing can be lengthened up to 5 km with a conventional graded index multimode fiber or up to 5.9 km with a single-mode fiber. It is confirmed by experiments that an optical transmission could be applied to a long distance and large capacity transmission system.