Calibration of Combined Mach–Zehnder Interferometers

A method for digital calibration of combined Mach-Zhender interferometers is developed and demonstrated experimentally. Error functions for each of the combined interferometers are evaluated in discrete space from a small number of measurements. Calibration into a maximum or a minimum of interference is achieved by maintaining collinearity between the electric field phasor of the two interferometers. The method applied here to an IQ modulator in a photonic integrated circuit is general and may be applied to combined interferometers for any application.