This paper describes the 8 B1H code used in 140 Mb/s long-distance digital fiber communication system and its designs in detail

with the emphasis on the simplification

reliability and the convinience of production and maitenance for the purpose of optical performance required for the whole system In the end

the system performance and the operating functions of the monitoring system for 140 Mb/s long-distance digital fiber communication system using 8B1H code is briefly described.