Abstract: A Bragg cell device for use as a tap in optical systems. In one embodiment an acoustic transducer is secured to a surface of an acoustic transmission medium, which is adjustably secured in hertzian contact with a surface of a waveguide. Bulk acoustic waves at frequencies above about 1 GHz are transmitted from the transducer through the transmission medium into the waveguide along a propagation path wherein the acoustic wavefronts intersect a light path in the waveguide at an angle which satisfies Bragg conditions, producing deflection of light out of the light path. Preferably, the transmission medium is also an optical conductor and is oriented upon the waveguide to receive the deflected light and transmit it to a polished optical window on the transmission medium. A grating transducer is secured on the transmission medium to detect acoustic signals reflected in the transmission medium.

Abstract: A fiber optic frequency shifter comprises an optical fiber having two propagation modes and an acoustic transducer for generating an acoustic wave. The transducer is positioned relative to the fiber to cause the wave fronts of the acoustic wave to acoustically contact the fiber at an angle of incidence which is less than 90.degree. greater than 0.degree.. Preferably, the wavelength of the acoustic wave is substantially equal to the beat length of the fiber times the sine of the angle of incidence.