High-frequency Measurement And Characterization On High-speed Electrooptic Phase Modulator

Electro-optic phase modulator is the simplest structure of Electro-optic modulator,and it has been popularly employed in optical communications, microwave photonicsand other fields with lower insertion loss and no need for bias voltage compared withintensity modulator. The half-wave voltage is one of the most important parameters. Inthis thesis, several half-wave voltage approaches for measurement electro-optic phasemodulator were investigated, and high-frequency characteristics of phase modulator willbe derived from measurement methods.Optical spectrum analysis approach is used to measure half-wave voltage of theelectro-optic phase modulator. It contains carrier nulling method and relative firstsideband/carrier intensity ratio method. Experiments are done and relationship betweenhalf-wave voltage and modulation index is obtained. Analytical expression of half-wavevoltage is derived at small signal approximation limit.Heterodyne approach of measuring phase modulator half-wave voltage isperformed. There are two approaches presented, one is relative intensity ratio methodbetween different-order sidebands, the other is relative intensity ratio method between thesame-order sidebands. Half-wave voltages are derived at low-frequency and with highresolution of modulation frequency by the first method. With the second method,influence of photoelectric detector and microwave amplifier’s frequency response iseliminated. Compared with optical spectrum analysis approaches, the agreement hasdemonstrated accuracy of heterodyne approaches.FM-IM approaches are presented to measure phase modulator half-wave voltage. Itcontains FM-IM spectral analysis method and FM-IM optical power analysis method.Simulations are done for the two methods through polarization maintaining optical fiberand tunable delay interferometer. The results agree with optical spectrum analysis’ andinfluence of delay time is analyzed. Polarization maintaining optical fiber delay time isobtained through interferometer approach.