Emulator of harmonic distortion of bias port of the mach-zehnder intensity modulator

The paper deals with the design of an analog circuit to substitute the role of a real intensity Mach-Zehnder modulator for the preliminary tuning of bias controllers. The proposed circuit has similar harmonic distortion as an electro-optic modulator biased around the quadrature operating point. The designed device utilizes a shaping circuit based on a differential pair of bipolar junction transistors. The harmonic distortion of both the Mach-Zehnder intensity modulator and the differential amplifier are analysed. A method to design the emulating circuit of desired features is described and explained and a the comparison of the measured results to the theory is presented.