Optical network packet error rate due to physical layer coding

A physical layer coding scheme is designed to make optimal use of the available physical link, providing functionality to higher components in the network stack. This paper presents results of an exploration of the errors observed when an optical gigabit Ethernet link is subject to attenuation. The results show that some data symbols suffer from a far higher probability of error than others. This effect is caused by an interaction between the physical layer and the 8B/10B block coding scheme. The authors illustrate how the application of a scrambler, performing data whitening, restores content-independent uniformity of packet loss. They also note the implications of their work for other (N, K) block-coded systems and discuss how this effect will manifest itself in a scrambler-based system. A conjecture is made that there is a need to build converged systems with the combinations of physical, data link, and network layers optimized to interact correctly. In the meantime, what will become increasingly necessary is both an identification of the potential for failure and the need to plan around it.