Underwater Wireless Acousto-Optic Waveguide (UWAOW)

Abstract

The present study originated in the lack of research into achieving underwater total internal reflection (TIR) via the acousto-optic effect. The uniqueness of this technique exists in the fact that it is based on a high sound pressure level which induces a localised change in refractive index of seawater sufficient to achieve total internal reflection within the communication channel. Different transducer systems for generating the pressure wave have been investigated and take the form of a wave which may be either a standing wave, or a novel beamforming technique. The former is based on an array of transducers and with an acoustic mirror at the receiver in order to establish the standing wave. The alternative approach relies on the high intrinsic directionality of a novel beamformer where an annular transducer array is examined as an acoustic source. In this paper, the main characteristics of the acoustic optic waveguide will be presented. This will include both sound and light propagation in the ocean, TIR, novel beam propagation, the refractive index of water as a function of the externally applied acoustic pressure, and the acoustic technology. The modelled results, the limitations imposed by the challenging medium, and the system requirements required to obtain an Underwater Wireless AcoustoOptic Waveguide (UWAOW) will be also addressed.

Research on the characteristics of Klein–Cook parameter and diffraction efficiency of acousto-optic interaction for low-frequency ultrasonic in the liquid

“…the m-th diffraction efficiency is (13) At normal incidence α = 0, Eq. ( 13) becomes (14) Hence, the intensity of the m-th diffraction light can be described by (15) The diffraction mentioned above is called Raman-Nath diffraction, and the medium disturbed by the ultrasonic wave is similar to a plane phase grating.…”

“…XUE et al [13] presented a new method to measure the velocity of sound in pure water and seawater using Raman-Nath diffraction caused by the acousto-optic effect between the optical frequency comb and the ultrasonic pulse, and compared with the reference value, the measurement uncertainty can be well below 0.03 m/s. GIULIANO et al [14] achieved an underwater wireless acousto-optic waveguide (UWAOW) using the acousto-optic effect, which was based on a localised change in refractive index of seawater induced by a high sound pressure level. In their work, the speeds of sound underwater with different temperatures and depths, and the refractive index of water as a function of the externally applied acoustic pressure were studied.…”