Search

In order to transmit the communication services presently provided over an optical access network, a design of the optical transmission system of TCM/TDMA-PDS (Time Compression Multiplexing/Time Division Multiple Access-Passive Double Star) type is described. The gain control and timing extraction needed for TCM/TDMA transmission are clarified. It is shown that a transmission frame with a preamble is effective for these requirements. Further, design of the present frame is described. A design example of 49.152 Mbs TCM/TDMA-PDS system and the measured results are presented. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 85(7): 61–70, 2002; Published online in Wiley Interscience (www.interscience. wiley.com). DOI 10.1002/ecja.1112

For economical construction of access networks, the passive double star (PDS) transmission system using optical fiber is promising. In the PDS transmission system, multiplexing of different transmission systems is possible due to wavelength division multiplexing (WDM). This system has drawn attention because addition of new service is easily accomplished. In this paper, an approach is proposed that is effective for wavelength division multiplexing in PDS transmission systems. When several systems with different transmit/receive level differences are transmitted over one fiber by wavelength division multiplexing, the transmission line length and the number must be adjusted to the system in which the transmit/receive level difference is the smallest in the conventional method. Hence, the application range of the system is degraded. On the other hand, in this paper, a method is proposed in which the loss distributions can be independently designed by cascading several star couplers when each system is wavelength division multiplexed. The method's procedure, evaluation of the efficiency of the accommodations, and an experimental example of an actual system are presented. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 84(7): 66–73, 2001

The metal subscriber transmission cable is a cascade connection of cables with different core radius and line length. To realize a digital subscriber transmission equalizer with a high accuracy requires an equalizer which does not produce an equalization error because of differences of core radius or cable length. This paper presents a multiband AGC equalizer to absorb the difference of core radius and line length whereby the filter coefficients are determined so that the equalization is optimized at several frequencies. Also, its construction, control by DFT and the design for parameters based on linear programming are presented. Based on the results of those investigations, an equalizer is constructed. By a transmission experiment using the actual transmission line, the equalization ability was verified.

In the late autumn of 1858 a 23-year-old man arrived in Edo and settled down in the Nakatsu clan house in Tsukiji, at the east end of the city. This man, Fukuzawa Yukichi, had been ordered by the senior clan officer to assume the headship of the domain school. This was the start of Fukuzawa’s Keio Gijuku (Keio College), so named because it was started in the fourth year of the Keio era, in the midst of the Restoration turbulence. Keio College educated some 6300 men and produced some 500 graduates between the late 1850s and 1889. It was superseded by Keio University, founded in January 1890, which had produced 1047 graduates by 1910: 792 in economics, 132 in law, 68 in politics and 55 in arts.1 These figures show clearly that the university was overwhelmingly economics-orientated.

The metallic subscriber line is composed of the cascade connection of cables with different core radius and the openended branch line called bridge-tap. Previously, the line equalizer for such a line has been constructed by combining the f equalizer, which has the equalization function for the single core cable, and the DFE circuit. The DFE circuit has a structure suited to LSI implementation, but has a problem in that a decision error propagates to succeeding bits, since the result of the decision is fed back as the compensation waveform for the intersymbol interference. This paper proposes a line equalizer based on the DFE circuit, which includes the DFE pre-equalizer to stabilize the DFE circuit. The design principle is presented. More precisely, the error propagation in the DFE circuit is analyzed. Combined with the analysis of the subscriber line characteristics, the required characteristics for the DFE equalizer are shown. Then a discussion is made on the number of taps in the DFE circuit, which determines the scale of the DFE circuit. Finally, a design example is presented for 320 kbit/s TCM transmission-line equalizer based on the design method presented. By experiment, the desired characteristics are verified.

This paper describes the design philosophy of a line driver and an automatic line equalizer applied for a 200 kbit/s ping-pong transmission system using existing metallic pair cables. The semiimpedance matched line driver is appropriate from the viewpoints of transmitted pulse distortion and power consumption. The automatic line equalizer is composed of a frequency domain equalizer as well as a time domain equalizer. The frequency domain equalizer is used to compensate for wide line-loss variations, while the time domain equalizer is used to compensate for intersymbol interferences due to cable gage changes and bridged taps. The decision feedback equalizer is used as the time domain equalizer. Gain vs. frequency characteristics of the frequency domain equalizer and number of required taps of the decision feedback equalizer are determined to minimize intersymbol interferences due to deviations between automatic line equalizer characteristics and various line characteristics. As a result of the design, the 200 kbit/s ping-pong transmission system is operative for 99 percent of NTT's existing subscriber cables with 100 percent cable fill.