Research On Key Technologies And Applications Of Radio Over Fiber With Large Spurious Free Dynamic Range

Radio over fiber(RoF)technology puts the microwave signal into the optical carrier for processing and transmission,and it integrates the advantages of the microwave technology and the photonics technology.The RoF technology can extend the propagation distance of the microwave signal with high frequency and wide bandwidth,and provide a large bandwidth medium for large-coverage wireless access.The advantages of the RoF technology include wide bandwidth,high frequency,low transmission loss,easy reconfiguration,immunity to electromagnetic interference,fiber optic remote,being compatible with distributed architectures and so on.In the Fifth Generation communication system,the RoF technology can realize a centralized wireless access network with large bandwidth,reconfigurable frequency,wide coverage and large transmission capacity,which contributes to improving the fixed and mobile integration and narrow-width combination of the existing network,and promoting the construction of ubiquitous intelligent optical network system with large capacity,ultra-broadband and mass wireless device connection.In the future radar system,the RoF technology is the key for existing radar systems to break through the bottleneck of "high frequency and broadband".It can achieve the generation,processing,and transmission of the radar signal with large-bandwidth,high-frequency,and low-noise,which helps enhance the detection ability and the precision of the radar system,and support the build of future radar system and radar networking system with improved performance and new detection structure.The spurious free dynamic range,one of the most important measures to evaluate the performance of an RoF link,characterizes the gain,the nonlinear distortions,and the noise figure in the system,and determines the permitted input power range of the RoF system.However,the nonlinear distortions of the electro-optic modulator,the chromatic dispersion induced by the long-distance fiber transmission,and the photoelectric conversion efficiency will make an impact on the SFDR of an RoF system.The objective of this thesis is to improve and optimize the SFDR performance of the RoF system.The breakthrough points to increasing SFDR of an RoF system involve mitigating the third-order intermodulation distortions,compensating for the power fading induced by dispersion,and enhancing the photoelectric conversion efficiency.The novel schemes are proposed to refine the performance of the wired optical fiber transmission and wireless beamforming.The main works and innovations of this thesis are as follows:1.An optical double-sidebands modulation(ODSB)based on dual-polarization modulator,with the advantages of the traditional modulations including the optical single-sideband(OS SB),the carrier-suppressed double sidebands(CS-DSB)and ODSB,is proposed for radio over fiber(RoF)system.In the condition of preserving two optical first-order sidebands,the proposed system has the features of chromatic dispersion(CD)immunity and tunable optical carrier to sideband ratio(OCSR),which can realize long fiber transmission distance with improved power efficiency.It is realized by CS-DSB plus optical carrier(OC)modulation at two orthogonal polarization states.No CD-induced power fading and phase severe shaking of the RF signals appear after the long-distance fiber transmission.By optimizing the OCSR of the system,the output RF power efficiency of the proposed scheme realizes significant improvement when input RF powers and output optical powers are both fixed.Besides,the phases of output RF signals can be tuned continuously and independently by controlling the phases of the OCs.The experiment results show that the continuous 360°phase shifts of output RF signal over 5-25 GHz are both realized in the cases of the back-to-back and fiber transmission.Lastly,the possibility of generating a frequency doubling signal is also verified.2.A high power efficiency and dynamic range RoF link with suppressed dispersion-induced power fading is proposed,which is realized based on the dual-polarization dual-parallel Mach Zehnder modulator(DP-DPMZM).Compared to the previously reported back-to-back RoF,the proposed scheme can realize compensating the nonlinearity of modulator and CD after long-distance fiber transmission simultaneously,leading to a largely raised SFDR of RoF.Besides,the proposed system,with tunable OCSR,can also effectively improve the output RF power and power efficiency of the link at the same input optical power into PD.The SFDR of the link will be further increased after OCSR optimization.We conduct a proof-of-concept experiment.Results show that an SFDR of 103.2 dB·Hz4/5 for 13.73 GHz is achieved after compensating CD and nonlinearity,which is 32 dB higher than that of a conventional DSB assisted RoF.After OCSR optimization,the output RF power achieves 13-dB improvement,and the SFDR is further raised to 114.12 dB·Hz4/5.3.A novel linearized OSSB modulation with tunable OCSR is proposed and experimentally demonstrated.The OSSB modulation with OCSR is a promising and popular technique in wideband analog signal transmission and microwave signal processing,which can improve modulation efficiency and combat fiber chromatic dispersion.However,in all reported schemes for achieving OSSB modulation with tunable OCSR,the SFDR of the systems are all limited by the third-order intermodulation distortion(IMD3).Our object is to improve SFDR and suppress IMD3 without cost in a novel OSSB modulation with tunable OCSR.The proposed system consists of a primary channel and a secondary channel.In the primary channel,an OSSB modulation with tunable OCSR is implemented.In the secondary channel,the optical carrier and first-order sidebands are perfectly cancelled out,which can realize suppressing the ID3 without gain penalty.In this way,a large-SFDR OSSB modulation with tunable OCSR is realized.Experimental results exhibit that the IMD3 is significantly suppressed without gain penalty,and the output microwave signal power obtains about 11-dB improvement by optimizing the OCSR.A greatly increased SFDR of over 128 dB·Hz4/5 is achieved in the proposed system.4.A high power efficiency and large SFDR microwave photonic phase shifter(MPPS)based on multi-order optical sidebands vector process technique is proposed and experimentally verified.To suppress the nonlinear distortions in the MPPS schemes assisted by an electro-optical modulator,the proposed system utilizes the optical vector processor(OSP)to control the amplitude and phase of multi-order optical sidebands including the zero-order sidebands,first-order sidebands and second-order sidebands.By tuning the phase difference and power ratio between the zero-sidebands and first-order sidebands,the phase of the output wideband RF signals can be continuously and arbitrarily tuned,and the power of the output wideband RF signals can be significantly improved at the same received optical power.By processing the phase and amplitude of second-order sidebands,the IMD3 components among the output signals can be effectively suppressed at different phase shift values,leading to largely improved SFDR and the innovation different from the previous reported MPPSs.The principle of the proposed MPPS with improved power efficiency and SFDR is given,and the capacity of phase shifting,suppressing IMD3 and improving power efficiency are demonstrated respectively,the SFDR obtains over 20-dB improvement.