Abstract: We show, both experimentally and theoretically, that the loss of coherence of a long cavity optical coherence tomography (OCT) laser can be described as a transition from laminar to turbulent flows. We demonstrate that in this strongly dissipative system, the transition happens either via an absolute or a convective instability depending on the laser parameters. In the latter case, the transition occurs via formation of localised structures in the laminar regime, which trigger the formation of growing and drifting puffs of turbulence. Experimentally, we demonstrate that these turbulent bursts arc seeded by appearance of Nozaki-Bekki holes, characterised by the zero field amplitude and pi phase jumps. Our experimental results are supported with numerical simulations based on the delay differential equations model. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement