This invention concerns the telecommunications sector and more specifically that of digital communication systems, disclosing a new method for generating eye diagrams asynchronously. This method makes it possible, without the use of recovery techniques or clock-signal synchronization that normally require high-speed electronics and complex synchronization mechanisms, to monitor signal quality (related to measurements of the quality factor Q) or performance quality (related to the degree of impact that signal-transmission impediments, such as crosstalk between channels and scattering,, inter alia, have on the communication system) of the communication channel, regardless of the transmission rate or modulation format and without prior knowledge of either of the two parameters mentioned. This method uses a power splitter that splits the power of the data signal into two parts, sending each of the two parts to two branches, the first branch being linked to a sampling and on-screen-display device (such as an oscilloscope) and the second branch being connected to a differentiator that differentiates the signal over time and also sends it to the sampling and on-screen-display device. The samples taken from the first branch are preferably shown as a function of the samples taken from the second branch, the first branch being the ordinate and the second branch being the abscissa of a point shown in a two-axis system.