Coaxial optical-fiber frequency shifter.

Area of Science:

• Photonics and Optical Engineering
• Acousto-Optics
• Fiber Optics

Background:

• Coupling polarization eigen-modes in birefringent fibers is crucial for optical signal processing.
• Existing free-fiber frequency shifters often lack robustness due to their T-junction design.
• Acoustic waves can be used to modulate optical properties in fibers.

Purpose of the Study:

• To demonstrate a rugged fiber-optic frequency shifter.
• To utilize a traveling torsional acoustic wave for mode coupling.
• To improve the mechanical stability of acousto-optic fiber devices.

Main Methods:

• A coaxial configuration was employed, integrating the acoustic-wave generator and a highly linearly birefringent optical fiber.
• Traveling torsional acoustic waves were used to induce coupling between polarization eigen-modes.
• Electrical drive power was applied to an acoustic transducer to generate the acoustic wave.

Main Results:

• A frequency shift of 3.204 MHz was successfully achieved.
• An optical coupling efficiency of 12% was obtained.
• The coaxial design demonstrated improved ruggedness over T-junction configurations.

Conclusions:

• The demonstrated coaxial fiber-optic frequency shifter offers a more robust alternative to existing designs.
• Traveling acoustic waves are effective for achieving polarization mode coupling and frequency shifting in optical fibers.
• The device shows potential for applications requiring stable and efficient acousto-optic modulation.