  Studying transition to a highly disordered state of turbulence from a
linearly stable coherent laminar state is conceptually and technically
challenging and immensely important, e.g. all pipe and channel flows are of
that type. In optics, understanding how systems lose coherence with increase of
spatial size or excitation level is an open fundamental problem of practical
importance. Here we identify, arguably, the simplest system where this
classical problem can be studied: we learnt to operate a fibre laser in laminar
and turbulent regimes. We show that laminar phase is an analogue of a
one-dimensional coherent condensate and turbulence onset is through a spatial
loss of coherence. We discover a new mechanism of laminar-turbulent transition
in laser operation: condensate destruction by the clustering of dark and grey
solitons. This is important both for the design of devices exploiting coherent
dynamics and for conceptually new technologies based on systems operating far
from thermodynamic equilibrium.
