Optical Frequency Comb Generation Based On External Modulator And Its Application In Satellite Communication

Microwave photonics,as a emerging disciplines which combines the unique advantages of microwave technology and photonics,is widely used in the fields of integrated radio frequency,satellite communication and microwave photonic radar.Optical frequency comb,as the connection center between microwave and light-wave,is an important part of signal generation in microwave photonics system.Therefore,how to generate flat optical frequency comb with adjustable spectral line spacing,ideal number of comb lines and high out of band rejection ratio has become a research hotspot.Therefore,it will focus on the generation of optical frequency comb based on external modulator and its application in satellite multi-band frequency conversion in this paper.The main work in this paper is as follows :(1)A scheme of generating optical frequency comb based on three cascaded DDMZMs is proposed.By controlling the amplitude and frequency of the multifrequency modulation signal added to the third stage DDMZM,the optical frequency comb with adjustable number of comb lines can be generated,and spectral line spacing can be flexibly adjusted to 4GHz or 6GHz.The results show that the flatness of 32 lines and 48 lines optical frequency combs is less than 0.5d B.(2)To optimize the power loss caused by too many cascading times in the former scheme,a scheme of optical frequency comb generation based on cascad ed DPMZM and DDMZM is proposed.In this scheme,the modulator and its cascade mode are changed to realize the generation of optical frequenc y comb,and the optical frequency comb with 36,42,44,54 and 66 lines can be obtained respectively,which significantly improves the number of comb lines.In this scheme,the spectral line spacing can be flexibly adjusted to 4GHz or 6GHz,the flatness is less than 1d B,and the out of band rejection ratio is greater than 18.71 d B.(3)A scheme of satellite multi-band frequency conversion based on reconfigurable single local oscillator optical frequency comb is proposed.In order to reduce the requirement of microwave photonic frequency conversion system on the frequency of electric local oscillator signal,the optical frequency comb is generated by using local oscillator frequency multiplication circuit,which can generate 2N microwave frequenc ies based on N comb lines.The results show that a K or Ka band RF signal can be converted to S,C,X,Ku,K,Ka,U and V bands in parallel,and realize the cross-band frequency conversion between Ka,K,Ku and X bands using this method.