Half-Wave Voltage Measurement Method Based on SI and Time-Domain Pulse Intensity Demodulation

A half-wave voltage
$(V_{\pi })$
measurement method for phase modulators (PM) based on Sagnac Interferometer (SI) and time-domain pulse intensity demodulation is proposed. The SI structure consists of a delay fiber and the PM to be measured. Through a structure of the fiber optic delay network, a pulsed light signal can be divided into four sensing signals. By using the time-domain pulse intensity demodulation method, phase information can be demodulated based on the intensities of four pulse signals, thereby obtaining the half-wave voltage. The
$V_{\pi }$
measured by this method is approximately 3.9V. When using an optical attenuator to increase the loss interference from 0 to 4dB in the transmission optical path, a relative standard deviation (RSD) of 2.1343% can still be obtained. The RSD of multiple measurements is 2.0948%. This method don’t require expensive instruments and can accurately and stably measure the half-wave voltage.