Feedforward linearization for RF photonic link with broadband adjustment-free operation

Area of Science:

• Photonics
• Electrical Engineering
• Radio Frequency Systems

Background:

• Nonlinearity in radio frequency (RF) photonic links, specifically the nonlinear transfer function of electro-optic modulation, limits dynamic range.
• Existing methods to suppress third-order intermodulation distortion (IMD3) often require complex link re-optimization when the RF carrier frequency is tuned.

Purpose of the Study:

• To propose and demonstrate an adjustment-free linearization technique for RF photonic links.
• To maintain a high spurious-free dynamic range (SFDR) across a broad band of RF frequencies without manual link adjustments.

Main Methods:

• A novel approach involving baseband extraction and re-modulation of distortion information.
• External modulation at a low bias point, followed by baseband processing to correct distortion.
• Theoretical analysis, simulation, and experimental validation of the proposed method.

Main Results:

• Demonstrated uniform suppression of IMD3 nonlinear spurs by approximately 60 dB.
• Achieved this suppression across a wide RF carrier tuning range (4 GHz to 12 GHz).
• Maintained a spurious-free dynamic range (SFDR) of around 125 dB (1-Hz bandwidth) without link re-optimization.

Conclusions:

• The proposed baseband distortion correction method offers effective and frequency-independent linearization for RF photonic links.
• This adjustment-free approach significantly enhances the dynamic range and simplifies the operation of RF photonic systems.
• The technique is suitable for advanced applications requiring stable high dynamic range performance during frequency tuning.