Microwave Photonic Frequency Conversion Technology Based On Cascade Modulation

Microwave photonic frequency conversion technology is widely used in broadband wireless access,satellite communications,electronic countermeasures and other fields.By using microwave photonic frequency conversion technology,frequency conversion on microwave signals can be achieved in the optical domain,which overcomes the traditional limitations of multiple frequency conversions,and has the advantages of anti-electromagnetic interference,anti-local oscillation leakage,and high frequency conversion gain.At present,the photonic frequency conversion technology has become a research hotspot,and it has gradually shown strong competitiveness in fields such as communications.Microwave photonic frequency conversion based on single electro-optic modulator has the disadvantages of crosstalk between local oscillator and radio frequency signals.Therefore,microwave photonic frequency conversion technology based on cascaded electro-optic modulators has caused extensive research.In this thesis,a microwave photonic frequency conversion system based on cascaded two Mach-Zehnder modulators is proposed,which can improve the spurious rejection ratio of the system by optical carrier separation and phase cancellation.The experimental results show that the spurious rejection ratio of the down-conversion signal generated by the link reaches 30.04 d B,the system conversion gain is(-55.3±0.4)d B,and the SFDR is94.0 d B.Hz^2/3.In addition,compared with the frequency conversion system using optical filters,the spurious suppression ratio is improved by 12.4 d B.On the other hand,since there are shortcomings of large size and poor reliability of the frequency conversion system built by discrete optical devices,microwave photonic frequency conversion systems based on integrated photonic chips have also been developed in recent years.Here,a microwave photonic down-conversion system based on cascaded Mach-Zehnder modulators and micro-ring resonator is proposed,where micro-ring resonator was used to perform optical filtering and frequency down-conversion.The experimental results show that the spurious rejection ratio of the down-conversion signal reaches 28.18 d B,the system conversion gain is(-43.1±0.2)d B,and the SFDR is 86.96 d B.Hz^2/3.