This paper introduces design of 140Mb/s long distance optical cable communication systems. From system model selected

the lengths of hypothetical reference digital link and digital section are chosen

then the properties of bit error and jitter are determined. Based on the practicability of networks

two types of line code

8B1H and 5B6B

are chosen

which are applied to two different systems. Furthermore

stress is laid on the approach to determine the major parameters of optical link and on the functions of auxiliary systems. Finally

the design of major specifications of data link for transmitting auxiliary signal by amplitude modulation of optical digital signal is introduced in detail.