Direct measurement of chirp parameters of high-speed Mach-Zehnder-type optical modulators

A method is described for measuring the chirp parameters and optical responses of Mach-Zehnder-type optical modulators by using an optical spectrum analyzer. The chirp parameter and the optical response for small-signal operation are expressed by the magnitude of the phase induced in each optical path of the Mach-Zehnder waveguides. The induced phase can be obtained from the ratio of the high-order optical harmonic intensities generated by large-signal operation in the millimeter-wave region. This method permits the chirp parameter to be evaluated at a specific frequency, while it is assumed to be independent of the frequency of the applied electric rf signal in the conventional method.