Switching time and switching capacity of acousto-optical switch

Acousto-optic switch can route optical signals in a branched fiber-optical network providing the input optical fiber switching to the output fiber-optic array. The principle of its work is based on light beam diffraction by ultrasonic wave, created in optically transparent media. The refractive index of an optical medium is altered by the sound frequency. Based on the acousto-optic deflector properties analysis, expressions defining acousto-optic switch capacity and switching time are deduced. Acousto-optic switch capacity is the number of switching channels, which are determined by the acousto-optic deflector resolution, namely the number of distinct light point in space, which provides the deflector at a discrete sound frequency change. The number of distinct points is determined by maximum angular range and the Rayleigh criterion - minimum angular intervals wherein two light points will be visible. Linking resolution characteristics and acousto-optic deflector parameters we obtained that the acousto-optic switch capacity is determined by the acousto-optic deflector aperture, the sound wave velocity, and the frequency operating range. The optical signal can’t be transmitted in less time than the acoustic wave travel through the solid media of the acousto-optic deflector. Therefore, the switching time is the value for which the acoustic wave passes through the optical field in the transverse direction.