Line codes and repeater fault location schemes for optical transmission systems

In this report, the line code structures of optical transmission systems are compared from the viewpoint of providing bit sequence independence (BSI). Repeater fault location schemes are also studied. Initially, we shall describe what considerations should be made to avoid consecutive identical codes as well as pseudo-synchronism in accordance with the inherent meaning of BSI, and we shall show a specialized code pattern to be considered for protecting pseudo-synchronism and a frame format to avoid pseudo-synchronism. Furthermore, we shall show the repeater fault location schemes for the phase-difference-detection type of CMI code transmission system and the m BIP code transmission system with odd parity, and we shall indicate how simple they are to realize. Then the transmission line code schemes of the 100 Mb/s optical cable transmission system are compared, and it is concluded that the preferable frame format is that in which frame synchronization pulses are inserted at positions different from the parity bits based on the 7 BIP code. In addition, experimental studies of the characteristics of the timing system in the repeater of the DF-100M system [1] will indicate the appropriateness of the design jitters and the selection of the frame format of the repeater.