Research On High-Resolution Frequency Domain Characterization Of High-Speed Optoelectronic And Photonic Devices

Rapid development of 5G technology,optical sensing and optical signal processing leads to a higher requirement of optoelectronic and photonic devices with high integration and multi-dimension spectrum manipulating ability.Therefore,high-resolution and multi-dimension frequency response characterization of optoelectronic and photonic devices is urgently needed.Optical spectrum analysis is a simple method to characterize optoelectronic and photonic devices.However,it is limited by the resolution of the grating,and cannot achieve a high-resolution measurement.Electrical spectrum analysis method by employing electro-optic modulation and optical-to-electrical conversion is a promising solution to achieve ultra-high-resolution magnitude and phase response measurement,which is beneficial for the design,manufacturing and application of optoelectronic and photonic devices.This thesis focuses on high-resolution frequency response characterization of the core devices in optical communication and microwave photonics system,such as narrowband optical filter,electro-optic modulator and the integrated electro-absorption modulated laser（EML）.The main contents of the thesis are summarized as follows:（1）An algorithm is proposed to retrieve the intrinsic phase response of an optical filter based on Kramers-Kronig relationship and Wiener-Lee transform.This method can be employed to obtain the intrinsic phase response of an optical filter by measuring its magnitude response only.Especially,this method avoids the phase introduced by the fiber pigtail and the free space coupling,which will submerge the intrinsic phase response of the optical filter,and cannot be easily eliminated by calibration.The kernel of this approach is based on the fact that the intrinsic phase response of an optical filter with a minimum phase response has a unique relationship with its magnitude response.Furthermore,the algorithm is realized by constructing the intermediate response function,since the magnitude response in Wiener-Lee transform must be an even function.The algorithm is verified by simulation and experiment,respectively.In the experiment,the intrinsic phase response of stimulated Brillouin scattering（SBS）in non-zero dispersion-shifted fiber（NZ-DSF）and single-mode fiber（SMF）,as well as stopband of phase-shifted fiber Bragg gratings（PS-FBG）,is retrived successfully from the its measured magnitude response.The proposed algorithm is also expended for the frequency domain characterization of microwave devices,which can improve the measurement efficiency and make it more cost effective.The phase response of microwave bandpass filter and 90°hybrid is obtained via using the proposed approach.Finally,the measurement error and application of the proposed algorithm are discussed.（2）An ultra-fast and high-resolution optical vector analysis scheme based on microwave photonics frequency-sweep is proposed,aiming to improve the measurement efficiency of point-by-point scanning characterization method,in which the measurement time is increasing with the improvement of resolution and measurement range.In the proposed scheme,a broadband frequency-sweep optical signal is generated by modulating a linear frequency-modulated signal on one radio-frequency（RF）port of a dual-drive Mach-Zehnder electro-optic modulator,which is used to achieve fast scanning of the frequency response characteristic of the device under test（DUT）.A single-tone microwave signal is injected into the other RF port of the modulator to realize frequency down-conversion of the frequency-sweep signal.The down-converted signal is then digitized by an analog-to-digital converter,and it is processed through Hilbert transform to extract the magnitude-frequency and phase-frequency responses of the DUT.In the proof-of-concept experiment,the magnitude-frequency and phase-frequency response of the stimulated Brillouin scattering gain of a section of NZ-DSF with a length of 3 km and the stopband of PS-FBG is measured,where the measurement time is only 20μs,and the frequency resolution reaches 20 k Hz.（3）A calibration-free frequency response measurement of high-speed electro-optic intensity modulator based on a dual-frequency optical carrier and a low-frequency detection is proposed.This approach avoids the requirement of more than one microwave sources,high frequency detection,and measurement error introduced by photodetector with uneven responsivity.In the proposed scheme,a dual-frequency optical carrier is generated by combining the carrier from laser diode with the acousto-optic frequency shifted one.A frequency-scanning single-tone microwave signal is injected into the push-pull Mach-Zehnder electro-optic modulator（MZM）which is working at carrier-suppressed double-sideband modulation mode.Hence,two frequency-scanning sidebands in upper and down with a fixed frequency interval are generated to carry the frequency response of MZM under test.Those optical frequency-scanning sidebands are photodetected into an electrical signal with a low frequency of acousto-optic frequency shift value.By using the proposed method,the frequency response of photodetector is eliminated,the efficiency of detection is improved,and the fluctuation of input microwave power is calibrated by measuring and deducting.The measurement error is theoretically analyzed through error transfer factor and mathematical expressions of output signal of MZM.Finally,the simulations for errors caused by fluctuation of input microwave power of MZM,and asymmetry divide ration of MZM are presented,respectively.（4）In order to investigate the optoelectronic interaction of electric-absorption modulated laser（EML）,a 3-port based equivalent circuit,which is combined with intrinsic network and parasitic network,is constructed.The intrinsic circuit model of distributed feedback（DFB）laser and electric-absorption modulator（EAM）are obtained via mathematical derivation from laser rate equations and quantum-confined Stark effect,respectively.Meanwhile,the parasitic network of EML is constructed from the analysis of package and fabricating of chip.Based on the measurement results of EML,the parameter values of each component in equivalent circuit are determined by iterative calculation.The scattering matrix of EML is simulated,in which the parameters S₁₂ and S₂₁characteristic the optoelectronic interaction inside the EML.Finally,the analysis of optoelectronic interaction inside the EML is achieved through simulation with different parameter values,including controlled coefficient K,coupling resistance R_g,and coupling capacitance C_g,which can influence the optoelectronic interaction inside EML.The proposed approach provides an analysis method for the design and application of integrated photonic devices.