The deployment of fiber optic systems has drastically altered the complexion of the digital network, and standardization of optical interface parameters has assumed paramount importance. This paper reports on the activities in various standards organizations, with emphasis on a synchronous network proposal which is currently being discussed in the T1 Committee.

A new class of nonparametric detectors based onm- interval partitioning is introduced. It is easier to treat analytically and implement practically than the widely used class of nonparametric detectors based on rank partitioning of the received signal space. In addition, these new detectors are robust or relatively insensitive to the underlying noise distribution. If the quantiles of the noise distribution are known exactly, the structure of the detector is particularly simple. Some general results for an adaptive system, when the quantiles of the noise distribution must be estimated, were also obtained.

In this paper, permutation channels, which include the rank channels and doubly uniform channels, are defined. A lower bound on the capacities of these channels is obtained with help of nonparametric signal-detection theory. This bound reduces to the actual capacity for memoryless doubly uniform channels by properly selecting the associated nonparametric detectors, The lower bounds on the capacities of the rank channels are expressed in terms of Kendalrs rank correlation coefficient. When the signal power is low, the comparison between a rank channel and a memoryless binary symmetric channel is expressed in terms of the Pitman-Noether asymptotic relative efficiency.