Microwave Photonic Frequency Conversion Based on a Wavelength Swept Laser

Youxue Kong,Bai-Ou Guan,Xinhuan Feng,Lin Wang,Yuan Cao,Guangying Wang

doi:10.3390/app10113813

Abstract

Microwave photonic frequency conversion, with flexible tunability and a simple structure based on a wavelength swept laser (WSL), is proposed and experimentally demonstrated. In the proposed frequency conversion system, a broadband WSL was used to generate a frequency-chirped optical carrier, which was sent to a Mach Zehnder modulator (MZM). A microwave signal, with its frequency to be converted, was applied to the MZM. The modulated signal was then sent to a dispersive device, where the waveform was compressed or expanded depending on the dispersion of the dispersive device. After photodetection, a frequency up-converted or down-converted microwave signal was generated. The tuning of the conversion frequency was achieved by adjusting the chirp rate of the optical carrier from the WSL or the dispersion of the dispersive device. The proposed approach was experimentally demonstrated. A microwave signal, with its frequency at 5 GHz, was up-converted to 5.577 GHz and down-converted to 4.936 GHz. The quality of the frequency converted microwave signal was also evaluated. The conversion performance could be further improved by introducing a WSL with a high duty cycle.

Highlights

The microwave frequency converter is one of the key components in microwave and millimeter-wave signal processing, including the transmitters and receivers of radio over fiber (RoF), the radar system and the reconnaissance and countermeasure systems [1,2,3,4,5]
We proposed a new all optical microwave photonic frequency conversion interrogation with flexible tunability and a simple structure based on a wavelength swept laser (WSL)
The conversion performance could be further improved by introducing a WLS with a high duty cycle

Summary

Introduction

The microwave frequency converter is one of the key components in microwave and millimeter-wave signal processing, including the transmitters and receivers of radio over fiber (RoF), the radar system and the reconnaissance and countermeasure systems [1,2,3,4,5]. Conventional frequency converters can be created by combining electrical mixers with tunable microwave sources or digital signal processing (DSP). Researchers proposed the use of the mode-locked pulse laser as the optical source for the frequency up-conversion system [18,19,20]. Laser as the optical source to realize sub harmonic up-conversion without external modulators [18]. We proposed a new all optical microwave photonic frequency conversion interrogation with flexible tunability and a simple structure based on a WSL. By tuning the optical characteristic of the WSL or the dispersion control device, the input signal could be up-converted to higher or down-converted to lower frequency with an arbitrary conversion coefficient and without an electrical tunable RF source. The conversion performance could be further improved by introducing a WLS with a high duty cycle

Frequency Conversion Principle

Simulations of Conversion Performance

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Conclusions