Wavefield control in multimode channels by the use of source arrays, with application to shallow-water sound

An intrinsic feature of the long-range signal propagation in random-inhomogeneous multimode waveguides is well known to be the signal loss and coherence degradation. These key factors are both dependent on the signal modal spectrum due to the fact that the signal-carrying modes essentially differ in their decay coefficients and effects on the signal fluctuations and the coherence length both in temporal and spatial domains (for a given distance from the source). Moreover, the output performance of signal processing against the nose background in such a scenario is also critical to the modal interference if this noise is intensive enough as is compared with the non-modal (for example, isotropic) ambient noise and/or sensor noise of the receiving system. In this paper, we give a short overview of our recent research focused on the effective wavefield control in multimode channels by the use of source arrays, the amplitude-and-phase distributions of which vary to control the signal modal spectrum at the channel ‘input’. The field experiments have been realized in a typical shallow-water sound channel, and their results show the practical application of the approach presented.