We present an optical fiber experiment in which we examine the space-time evolution of a modulationally unstable plane wave initially perturbed by a small noise. Using a recirculating fiber loop as experimental platform, we report the single-shot observation of the noise-driven development of breather structures from the early stage to the long-term evolution of modulation instability. Performing single-point statistical analysis of optical power recorded in the experiments, we observe decaying oscillations of the second-order moment together with the exponential distribution in the long term evolution, as predicted in [D. S. Agafontsev and V. E. Zakharov, Nonlinearity 28, 2791 (2015)]. Finally, we demonstrate experimentally and numerically that the autocorrelation of the optical power g (2) (τ ) exhibits some unique oscillatory features typifying the nonlinear stage of the noise-driven modulation instability and of integrable turbulence.Modulational Instability (MI), also known as Benjamin-Feir Instability, leads to the spontaneous breakup of plane waves into train of pulses. MI has been extensively studied in the last five decades, see e.g. [1,2], and is often seen as the exponential amplification of a weak modulation of a monochromatic carrier wave. This fundamental phenomenon arises in physical systems such as deep water waves [3], nonlinear optical waves [4], Bose-Einstein condensates and matter waves [5], which are described at leading order by the focusing one-dimensional nonlinear Schrödinger equationThe 1DNLSE is integrable and its exact solutions can be found by using the so-called "inverse scattering transform" (IST) [6,7]. For the MI driven by a sinusoidal perturbation of a constant background, the long-term spatio-temporal dynamics is described by breather solutions of the focusing 1DNLSE, such as the Akhmediev Breather (AB) [8][9][10][11][12][13][14][15]. However, natural perturbations are generally not sinusoidal modulations but rather represent a random process [16][17][18][19][20][21][22].Despite the numerous studies devoted to the subject of MI in optical fibers [4,23], it is only recently that single-shot observations of the noise driven MI have been reported. Shot-to-shot fluctuations of the optical spectra have been measured in experiments with light pulses in [20], while breather structures spontaneously emerging from noise superimposed to a continuous wave (CW) field have been reported in [22]. However, in these pioneering studies the spatio-temporal dynamics and the evolution of statistical properties of the light field along the fiber could not be recorded, since the observation was made only at the output of the fiber.From the theoretical point of view, the question of noise-driven MI enters whithin the fundamental framework of integrable turbulence, which was first introduced by V. E. Zakharov in [24] and is now a subject of extensive theoretical [19,[24][25][26][27][28][29][30] and experimental [31][32][33][34][35][36] research.In the long term evolution, the integrable turbulence is ...