The self-seeded cavity appeared in the last few years as a colorless and low cost solution for wavelength division multiplexing (WDM) access. Although the self-seeded source presents a simple architecture, its behavior has been misunderstood for a long time. In this paper, we explain its operating principles and why we can define such a source as a laser. We evidence a laser threshold and show cavity modes for various lengths. We describe the conditions required by the reflective semiconductor optical amplifier (RSOA) to sustain the self-seeded cavity, by evaluating the choice of its epitaxial structure and the influence of its optical confinement factor.
An analysis of the cavity behavior is given, pointing out that the relative intensity noise (RIN) results from the beating noise between the cavity modes. An overview over the last performances in the C- as well as in the O- band is then presented. Some practical applications are reported. In particular, we detail the mobile front-haul as a possible employment for the self-seeded cavity to achieve a self-organized wavelength network.