Wideband electro-optic phase modulator (PM) is a critical component for the applications of coherent optical communication

microwave photonics signal generation

processing and measurement

due to the advantages of bias-free

linear modulation and low insertion loss. Modulation index and half-wave voltage are key parameters to assess the performance of PMs. However

the conventional mothed based on optical spectrum analyzer (OSA) surfers from low and measurement dead-band. To overcome these problems

a self-calibrated and high-resolution method for the measurement of PM is proposed based on UV-ESA. The modulation index and half-wave voltage are achieved by analyzing the electrical beat notes of the detuned optical carrier and the phase modulation sidebandswith two different driving voltages in the same driving frequency. Moreover

it verify the validity of proposed mechod without dismantling the measurement link and eliminates the need of assisted wideband devices or instruments. The measured results are also compared with those based on OSA to check for effectiveness and consistency of accuracy.