Sideband Suppression High-Speed Measurement Link And High-Frequency Interface Circuit Design For Optical Modulator

Optical modulation technology is an essence of high-speed modern optical communication systems.The electro-optical phase modulator is one of the core devices in optical communication,optical signal processing and optical interconnection.The characterization of its frequency domain characteristics has important research significance for the optimization and evaluation of communication systems.This thesis focuses on the measurement methods of high-speed modulation characteristics(including key parameters such as modulation coefficient,half-wave voltage,etc.)of electro-optic phase modulators and the design of high-frequency interface circuits.The following research work is carried out:Firstly,the basic idea of measuring the high-frequency characteristics of the electro-optic phase modulator by the spectral analysis method is given.Typical spectral analysis methods include carrier nulling method and sideband intensity ratio method.The measurement the modulation coefficient and half-wave voltage of the electro-optic phase modulator by the sideband intensity ratio method is simulated.The method is simplified as the calculation complexity reduces under a small signal approximation circumstance.Then,the principle of phase modulation-intensity modulation(PM-IM)conversion based on the basic idea of measuring the high-frequency characteristics of electro-optic phase modulators is described,and a simple and convenient sideband suppression measurement system for the electro-optic phase modulator is designed.The system use the narrow-band filtering characteristics to break the sideband amplitude balance of the phase modulation signal to implement the PM-IM conversion.The simulation verifies the feasibility of the measurement system and the measurement errors analysis mainly arise from the filter components and the photoelectric conversion.Tackling with the former,a dual-light source method is proposed to reduce the test error.Next,the basic idea of optical heterodyne method for measuring the high-frequency characteristics of electro-optic phase modulators is analyzed.The optimization method of optical heterodyne—self-heterodyne analysis method is introduced.Two basic test methods of frequency-shifted self-heterodyne and phase-shifted self-heterodyne are verified by simulation.A dual-source phase-shifted self-heterodyne measurement method based on the latter is invented.This method can not only depict the modulation coefficient and half-wave voltage of the electro-optic phase modulator,but also the modulation phase value and its linearity.The feasibility and accuracy of the designed measurement method is validated so that it can realize self-calibration,high-resolution,and high-precision measurement of the electro-optic phase modulator.After that,the measurement procedure of the electro-optic phase modulator chip is investigated.High-frequency bias-interface circuitry for the input of microwave signals is designed and verified.Finally,the whole work is summarized and some prospects are suggested.