Research On Ultrahigh-resolution Optic-Electro/Electro-Optic Vector Analysis

The frequency response(including amplitude response and phase response)of microwave photonic devices is an important parameter to characterize optic-electro/electro-optic conversion efficiency and amplitude and delay response characteristics.The measurement of "ultra-high resolution","large bandwidth" and "high precision" of microwave photonic devices has become the key to the development and production of microwave photonic information system.The traditional optic-electro/electro-optic vector analysis technique has low resolution and accuracy,which is difficult to meet the current and future high performance microwave photonic system test requirements.Therefore,it is urgent to carry out the research on ultra-high resolution optic-electro/electro-optic vector analysis,so as to measure the frequency response of high-performance microwave photonic devices like high-speed photodetector and high-speed electro-optical modulator.In this paper,a method of ultra-high resolution optic-electro/electro-optic vector analysis based on microwave photonics technology is proposed to realize the vector analysis of high-speed photodetector and phase modulator.The specific research work is as follows:In order to solve the problem of high resolution vector analysis of optic-electro components,a vector analysis method based on frequency shift carrier and double sideband modulation is proposed.The asymmetric double sideband signal is converted into photocurrent by the device under test.This method can measure not only the frequency response of high-speed photodetector but also the frequency response of optical coherent receiver.Benefiting from the high-finesse frequency sweeping,the frequency resolution can be up to sub-Hz theoretically.The experiment accurately measured the frequency response of the high-speed photodetector and the optical coherent receiver,with the frequency resolution of 10 MHz and the measurement bandwidth of 49.99 GHz.For the sake of solving the problem of high resolution vector analysis of phase modulator,a vector analysis method based on phase modulation-intensity modulation conversion technique is proposed.The PM-IM converter is used to convert the phase modulated signal into the intensity modulated signal,which is then sent to the photodetector with known frequency response and measure the overall response of the system.Removing the PM-IM converter and photodetector response,the frequency response of the phase modulator is obtained.Theoretically,the resolution can be sub-Hz.In the experiment,the amplitude and phase response of the high-speed phase modulator was accurately measured with a frequency resolution of 10 MHz and a measurement bandwidth of 41.99 GHz.In order to improve the dynamic range,a high speed phase modulator frequency response measurement based on stimulated brillouin scattering was proposed.The frequency resolution was 5 MHz,the measurement bandwidth was 49.99 GHz,and the dynamic range was improved by 17.74 dB.