The dynamics of semiconductor lasers are modelled in the time domain using a pair of differential equations known as rate equations. The analysis, based on temporal solutions of these equations, yields practical results utilised in various applications. Alternatively, an analysis employing the phase space method, a well-established analytical tool in applied mathematics, provides a more comprehensive perspective on semiconductor laser dynamics. The main purpose of this paper is to provide a detailed and intuitive introduction to phase space analysis in the context of semiconductor laser dynamics. The goal is to offer an easily comprehensible description of the mentioned method, placing emphasis on the graphical representation and physical interpretation of the results. The method effectiveness is shown through its application to selected practical problems. Furthermore, semiconductor laser dynamics can be treated as an illustrative example, showcasing the applicability of the method, which can be readily extended to other types of lasers or even more advanced dynamic systems.

Self-swept erbium fiber laser emitting around 1.56 μm is reported in detail. Both sweep directions were registered: pointing toward longer and shorter wavelengths, redshift and blueshift sweeping, respectively. We describe method of determining the direction of the wavelength drift using the monochromator based optical spectrum analyzer. Possible root for this sweeping regime, i.e., the gain modulation along active fiber, is discussed with the help of a simple model calculating the overall cavity gain that can predict the direction of the laser wavelength sweeping.