All-optical serrodyne frequency shifter

Area of Science:

• Photonics
• Optical Engineering
• Nonlinear Optics

Background:

• Serrodyne-like optical frequency shifting is crucial for applications like coherent optical communications and radar systems.
• Existing electro-optic methods often require complex, high-bandwidth electrical signals and can introduce losses and polarization dependence.

Purpose of the Study:

• To develop and demonstrate a novel all-fiber method for generating a single-sideband serrodyne-like optical frequency shift.
• To overcome the limitations of electro-optic approaches by proposing a simpler, more robust optical solution.

Main Methods:

• Utilizing cross-phase modulation in a nonlinear optical fiber to create a time-varying phase shift.
• Employing a simple pulsed pump laser to drive the nonlinear process.
• Designing an all-fiber device for integration and ease of use.

Main Results:

• Successfully demonstrated a 150 MHz optical frequency shift at 1550 nm using the proposed all-fiber device.
• Achieved a low insertion loss of 1.5 dB.
• The frequency shifter was polarization-independent.

Conclusions:

• The developed all-fiber method provides a viable, low-loss, and polarization-independent alternative for optical frequency shifting.
• The technique shows potential for scaling to multi-GHz shifting frequencies, broadening its applicability.