Optical performance monitoring based on asynchronous amplitude histograms

Abstract

This work has shown that by using simple analysis techniques, such as the average Q-factor, one may employ asynchronous histograms to derive information that would otherwise require a complete optical receiver as well as a BER counter to estimate. More complex techniques, such as the decomposition of asynchronous histograms, allow handling signals that suffer from distortion to the point where the original signal format is unrecognizable. In addition, it has been shown that histogram comparison techniques either using theoretical histograms or reference histograms can be used to extract information on the signal under analysis. Some practical aspects on the design of asynchronous sampling systems for the acquisition of asynchronous histograms have been considered. In particular, the most demanding aspect has been shown to be the sampling aperture time. It has been shown that the aperture time of the sampling system conditions the performed measurement by restricting the noise or distorting the signal under analysis. As a consequence, compensation methods have to be used either by adjusting the performed measurement or by using reference histograms. In summary, the analysis of asynchronous histograms has survived the evolution of optical communications systems as an effective proposal for advanced optical performance monitoring thanks to its remarkable flexibility. Asynchronous histogram acquisition systems can be easily designed for very wide ranges of bit rates and arbitrary signal formats. An extensive set of simple and robust methods to analyze asynchronous histograms has been developed over the years, and application to novel modulation formats can be carried out with relatively little effort.