A process for the measurement of the half wave voltage of an optical modulator of the mach - zehnder - type

摘要

A method and a device for measuring the half-wave voltage of a Mach-Zehnder type optical modulator accurately and without depending on the bias variation of an optical modulator. The method of measuring the half-wave voltage of the Mach-Zehnder type optical modulator comprising the steps of applying a high-frequency AC signal (34) and a monitoring low-frequency AC signal (35) in a superimposed manner to a Mach-Zehnder type optical modulator (1), or applying the both respectively to separately constituted electrodes, and observing the low-speed response of an output light from the optical modulator (1), wherein the half-wave voltage at a frequency to be measured of the Mach-Zehnder type optical modulator (1) is measured by using the voltage amplitude of the high-frequency AC signal (34) when the intensity change of an output light by the monitoring low-frequency AC signal (35) is almost zero with the voltage amplitude of the high-frequency AC signal (34) kept variable.