Filter-free photonic microwave upconverter with frequency quadrupling

Area of Science:

• Photonics
• Optical Communications
• Signal Processing

Background:

• Frequency upconversion is crucial for extending the range of optical communication systems.
• Existing methods often face limitations in bandwidth, efficiency, or complexity.
• Novel approaches are needed to enable higher frequency generation for advanced applications.

Purpose of the Study:

• To present and experimentally demonstrate a novel method for optical frequency quadrupling.
• To utilize an integrated polarization-division multiplexing dual-parallel Mach-Zehnder modulator (PDM-DPMZM) and an intensity modulator (IM) for this purpose.
• To achieve efficient and high-quality frequency upconversion for advanced signal generation.

Main Methods:

• A PDM-DPMZM is employed to generate polarization-multiplexed second-order sidebands by controlling bias voltage.
• A polarization controller aligns specific sidebands with the axes of an IM for selective modulation.
• An upconverted signal with quadrupled frequency is generated at the photodetector.

Main Results:

• The demonstrated method achieves a working bandwidth of 6-40 GHz.
• A spur suppression ratio of 37.5 dB is obtained for the upconverted signals.
• The conversion efficiency is measured at -32 dB, with successful generation of 100 MSym/s QPSK/16QAM signals at 26 GHz.

Conclusions:

• The proposed scheme offers a novel and effective approach for optical frequency quadrupling.
• The experimental results validate the feasibility and performance of the method.
• This technique has potential applications in high-frequency signal generation for optical networks.