Research On Frequency-Doubling Optoelectronic Oscillator Based On Dual-Polarization Modulator

With the advent of the information age,people have been exploring how to use optic and radio frequency technology to solve the problems encountered in the development of communication and information technology.Microwave photonics has developed rapidly during this period.As an important part of microwave photonics,the optoelectronic oscillator(OEO)can effectively break the"electronic bottleneck"and has become a research hotspot.Compared with traditional oscillators,OEO has the advantage of being able to generate better quality microwave signals,with low phase noise,large frequency tuning range,high spectral purity and anti-electromagnetic interference.However,the operation frequency generated by the OEO is usually restricted by the bandwidth limitation of the components used in the OEO.Therefore,frequency-doubling optoelectronic oscillator(FD-OEO)can overcome the restriction of the operation frequency,which has important scientific and practical significance.This thesis starts from the background and then introduces the value and significance of OEO.Subsequently,the contributions to the OEO frequency-doubling system in recent years by researchers are introduced.After that,the contents in this article are introduced.Then the working principle of the classic OEO model is introduced in detail,and the three key characteristics of OEO are theoretically analyzed.The key components in the frequency multiplier optoelectronic oscillator are also introduced.Finally,two methods for realizing frequency-doubling optoelectronic oscillators based on dual-polarization modulator are proposed and experimentally demonstrated:1.An approach of the carrier suppression is employed to realize the frequency-doubling optoelectronic oscillator.X-MZM works at the minimum transmission to achieve the carrier-suppressed double-sideband(CS-DSB)signal,and Y-MZM works at the maximum transmission to obtain the optical carrier signal.The two polarization directions of the two optical signals are orthogonal.In the OEO loop,after the polarization operation for the two polarization orthogonal signals,the polarization directions of the two signals are again consistent,and a common double sideband(DSB)signal with an optical carrier is generated.The oscillation frequency is selected by an electric filter,and the oscillation signal with the fundamental frequency is generated.In the frequency-doubling branch,only the CS-DSB signal in the X direction is allowed,and the frequency-doubling signal is obtained after photodetection.In the experiments,the system can output a frequency-doubling signal with a tunable frequency and a suppression ratio of 41 d B.2.An approach of the carrier cancellation is employed to realize the frequency-doubling optoelectronic oscillator.X-MZM works at the quadrature transmission to get the DSB signal with an optical carrier.Y-MZM works at the maximum transmission to obtain the optical carrier.In the OEO loop,after the polarization operation for the two polarization orthogonal signals,the DSB signal with an optical carrier is obtained.After frequency selection by the filter,the fundamental frequency oscillation signal is obtained.In the frequency-doubling branch,after polarization operation,the optical carriers of the two polarization orthogonal signals are canceled,and the CS-DSB signal is obtained.Thus the frequency-doubling signal is obtained after photodetection.The experimental results show that the suppression ratio of the frequency-doubling signal is about40 d B,the phase noise is-91.25 d Bc/Hz,and the stability is 2.3×10^-7.