We have demonstrated an experimental setup for the coherent phasing of a seven-channel fibre laser system ( λ = 1064 nm) in a scheme comprising a master oscillator and a set of parallel amplifiers with lithium niobate-based fibre-optic phase modulators. Using a stochastic parallel gradient algorithm, an instrumental phase modulator control unit ensures a bandwidth of the system up to 450 kHz. The effectiveness of phasing of light transmitted through a turbulent medium with a characteristic time scale τ turb has been studied experimentally as a function of phasing time τ ph. The results demonstrate that the average Strehl ratio begins to rise at τ turb/τ ph ⩾ 2 and that the effectiveness of compensation for dynamic phase distortions in the beam propagation path rises sharply at τ turb/τ ph ≈ 20. For τ turb/τ ph ⩾ 30 – 40, the average Strehl ratio remains constant at the level reached.

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