A simple in-service error detection scheme based on the statistical properties of line codes for optical fibre systems

An investigation has been carried out into the practicability of adapting a scheme of in-service error monitoring at dependent repeaters, currently used on British Telecom 140 Mbit/s coaxial cable systems, for possible incorporation in the supervisory subsystem of future generation 140 Mbit/s optical fibre digital line systems. Attention has been focused on the use of the technique in systems employing binary alphabetic line codes of the form mBnB. In particular, in-depth studies on the performance of the error-detection circuit for 7B8B line codes, which are attractive for 140 Mbit/s optical systems, are reported.