The purpose of this paper is to present a detailed characterization of a dual-wavelength VCSEL - the BiVCSEL. This device consists of two active optical cavities, which share a coupling mirror and can be independently electrically pumped. We present the output powers for the two emitted wavelengths (short - lambda(S), long - lambda(L)) versus the currents in the two cavities (I-TOP, I-BOT). These (lambda(S), lambda(L))-(I-TOP, I-BOT) maps identify the different regimes of operation of the BiVCSEL: emission at only one wavelength (either short or long) and dual-wavelength emission, each domain being delimitated by the threshold curves. These curves are passing through a single point, which identify the dual-emission threshold (I-TOP(th), I-BOT(th)). The apparition of a parasitic lasing mode due to the oxide apertures will be also presented as well as the competition between this mode and the designed lasing modes of the structure.