A new cell loss recovery method is proposed for use with the virtual paths (VPs) of asynchronous transfer mode (ATM) networks. Its advantages over conventional methods on virtual circuits include reduced coding/decoding delays and facility sharing. In addition to its consecutive cell loss compensation ability, another feature of this method is that cell loss compensation facilities are only required at VP terminating nodes. Performance estimations show a large reduction in cell loss rate.>

A cell loss recovery method to be applied to the virtual paths (VPs) of asynchronous transfer mode (ATM) networks is introduced. The method uses forward error correction (FEC). Its advantages over conventional methods on virtual circuits (VCs) include reduced coding/decoding delays and facility sharing. In addition to consecutive cell loss compensation, another feature of this method is that cell loss compensation facilities are only required at VP terminating nodes. When a cell is discarded due to buffer overflow, successive cells also tend to be discarded. Performance estimations show an outstanding reduction in cell loss rate.>

The structure of the error correction coding schemes and a reconstruction method for lost cells are derived. The performance analysis includes transmission efficiency, interleave delay, and cell loss compensation performance. The results show that effective compensation performance, with high transmission efficiency and small interleave delay, is obtained by applying the proposed coding parameter selection. The cell loss compensation schemes yield high-quality performance with low cell loss probability.>

A multiservice fiber-optic subscriber system using wavelength division multiplexing technology has been developed by Nippon Telegraph and Telephone Corporation to provide both 64 kbits/s and broad-band communication services on a single multimode fiber. The subscriber network is formed in a star topology to facilitate bidirectional connection. The system was put in service in March, 1985, as part of the information network system (INS) model system. This paper describes the configuration and characteristics of the video distribution system of this fiber-optic subscriber system. The distribution system uses analog baseband video transmission at a 0.89μm wavelength. The video channel selection is made by an FDM video tuner installed in a central office. The overall performance successfully met design objectives.

Investigations are carried out on the performance of video transmission systems employing square wave frequency modulation (SWFM). A simple formula for the signal-to-noise ratio (SNR) in the SWFM video transmission systems is derived. The SNR performance is compared to that of frequency modulation (FM) and pulse frequency modulation (PFM). SWFM is shown to display the greatest receiver sensitivity when the fiber 6 dB bandwidth is less than 100 MHz. Video transmission experiments demonstrate the advantages of the SWFM, including 1) degree of simplicity in modulation/demodulation circuits as well as in optical transmitter and receiver circuits, 2) tolerance to nonlinearities in the system, and 3) insensitivity to the fiber baseband frequency-phase characteristics. Both the theoretical and experimental results have made clear the superiority of SWFM optical video transmission systems in application to CATV distribution systems and subscriber loop systems.

Investigations are carried out on the SNR performance in fiber optic FM transmission systems which use multimode fibers and 1.3 μm laser diodes. Both laser diode noise and modal noise are quantitatively evaluated in systems with and without employing a superimposed pulse modulation scheme. Based on these investigations, parameters for analog-digital hybrid signal transmission systems employing FM are determined. The hybrid signal consists of audio, video, and 2 Mbit/s digital data. The results obtained in transmission experiments satisfied the design objectives and confirmed the technical feasibility of an analog-digital hybrid transmission employing FM. The obtained results make the fiber optic FM transmission system with a 1.3\mumLD an attractive alternative in subscriber systems, and video transmission systems for microwave IF links and CATV trunks.

One- and two-way 6.3 Mbit/s optical transmission systems employing wavelength-division-multiplexing (WDM) are designed for application to telephone networks. Multiplexing at two wavelengths, 1200 and 1300 nm, as well as that at 810 and 890 nm, is found to be effective after taking the application fields and present fabrication techniques for optical multiplexers into account. Requirements for optical multiplexers are clarified through SNR design in which crosstalk is dealt with effectively. Optical multiplexers composed of newly developed dielectric multilayer thin-film filters are designed to meet the systems' requirements, and good transmission quality is confirmed for the systems by experiments.

The design and performance of an experimental 800 Mbit/s repeater for four-level digital transmission over a coaxial cable is described in this paper. The 800 Mbit/s digital system exceeds the 60 MHz analog system, both in capacity and in economy. The repeater is designed to operate in repeater housings located at 1.6 km maximum spacing to be compatible with the 60 MHz analog sytsem. A nonredundant four-level line code has been employed, using a newly developed quantized feedback dc restoration technique. The most important item in realizing the high-speed multilevel repeater is the reduction of intersymbol interference. A simple quantized feedback scheme and an adjustable three-tap transversal equalizer have been used to compensate for intersymbol interference. The experimental repeater has been tested for 1.1-1.7 km repeater spacings using 2.6/9.5 mm coaxial cable. The results show that an 800 Mbit/s repeater with 1.6 km maximum repeater spacing is feasible.