Focused acoustic wave fiber optic reflection modulator

An acousto-optic device comprising,

• an optical fiber waveguide for propagating an optical carrier signal along an optical path,
• an in-fiber grating located on a line near the central core of the optical fiber of said optical fiber waveguide,
• carrier signal generating means providing an optical carrier signal to said optical fiber waveguide,
• a focused acoustic wave transducer for modulating the optical carrier signal, said transducer including,
• an inner electrode having an inner surface at least partially surrounding and in energy transfer relation with the optical fiber and an outer surface,
• a thin shell of electromechanical conversion material having an inner and an outer surface with its inner surface being in energy transfer relation with the outer surface of said first electrode,
• an outer electrode having an inner and an outer surface with its inner surface in energy transfer relation with the outer surface of said thin shell, and
• electrical signal generating means connected to said inner and said outer electrodes and operable to apply an electrical signal across said thin shell of electromechanical conversion material to thereby produce inwardly and outwardly directed acoustic waves in said inner and said outer electrodes, respectively,
• said inner electrode having a thickness and shape to focus said inwardly directed acoustic waves along said line at the optical fiber central core containing said grating to induce strain producing a proportional change in the refractive index of the optical fiber waveguide to produce a reflection spectrum shift in the grating, at the line of focus whereby the reflection change produces a grating reflection change for a narrow bandwidth optical signal on a skirt of the grating spectrum and thereby modulate the optical carrier signal,
• said outer electrode being formed of a material and having a thickness such that said outwardly directed acoustic waves are substantially completely attenuated therein.

An acousto-optic device comprising, an optical fiber waveguide for propagating an optical carrier signal along an optical path, an in-fiber grating located on a line near the central core of the optical fiber of said optical fiber waveguide, signal generating means providing an optical carrier signal to said optical fiber waveguide, a focused acoustic wave transducer for modulating the optical carrier signal, said transducer including, an inner electrode having an inner surface at least partially surrounding and in energy transfer relation with the optical fiber and an outer surface, a thin shell of electromechanical conversion material having an inner and an outer surface with its inner surface being bonded to the outer surface of said first electrode, and an outer electrode having an inner and an outer surface with its inner surface in energy transfer relation with the outer surface of said thin shell, and signal generating means connected to said inner and said outer electrodes and operable to apply an electrical signal across said thin shell of electromechanical conversion material to thereby produce inwardly and outwardly directed acoustic waves in said inner and said outer electrodes, respectively, said in-fiber grating having a spectrum capable of being shifted from a fully transmitting grating to a fully reflecting grating for a given narrow band optical signal by application of strain resulting from a focused acoustic wave from said focused acoustic wave transducer to thereby produce an acoustic wave optical switch for controlling the exit direction of an optical signal entering said grating, and wherein said signal generating means is operable to provide a switching signal to said focused acoustic wave transducer to produce a focused acoustic wave shifting said grating between said fully transmitting and said fully reflecting spectra.

A method of modulating an optical signal passing through an elongated optical fiber waveguide comprising:

• providing an in-fiber grating on a line near the central core of the optical fiber of the optical fiber waveguide,
• directing an optical carrier signal longitudinally through the optical waveguide,
• providing an inner electric conductor having an inner surface at least partially surrounding and in energy transfer relation with the external surface of the optical fiber of the waveguide, and an outer surface,
• providing a thin shell of electromechanical conversion material having an inner surface and an outer surface, with said inner surface bonded to the outer surface of the inner electrical conductor,
• providing an outer electrical conductor having an inner surface in contact with said outer surface of said thin shell of electromechanical conversion material, and
• applying a high frequency electrical signal across said thin shell of electromechanical conversion material through said inner and outer electrical conductors to thereby produce inwardly and outwardly directed high frequency acoustic waves in said thin shell of electromechanical conversion material and in said inner and said outer electrical conductors, respectively,
• said inner electrical conductor having a thickness and shape to focus said inwardly directed acoustic waves along the line containing the in-fiber grating to induce strain producing a proportional change in the refractive index of the waveguide of the optical fiber waveguide to produce a reflection spectrum shift in the grating at the line of focus whereby the reflection shift produces a grating reflection change for a narrow bandwidth optical signal on a skirt of the grating spectrum, and thereby modulates the optical carrier signal,
• said outer electrical conductor being formed of a material and having a thickness such that outwardly directed acoustical waves are substantially completely attenuated therein.