Modeling of the static and dynamic responses of an integrated laser Mac-Zehnder modulator and comparison with an integrated laser EA modulator

In an integrated laser Mach-Zehnder modulator (ILMZ), as well as in an integrated laser electroabsorption (EA) modulator (ILM), optical feedback can lead to a high level of frequency chirp and relaxation oscillations, compared to the case of a laser coupled into a discrete external modulator through an optical isolator. To investigate these aspects, in the particular case of the ILMZ, an original model has been developed. Analytical expressions of the frequency modulation (FM) and amplitude modulation (AM) responses of two types (2×1 and 2×2 output couplers) of ILMZ are given by the model, and the direct and indirect contributions to the FM responses are identified. The model can be used in the design and optimization of the ILMS, aiming at a small optical frequency chirp and small AM perturbation at resonance frequency. Numerical simulation of the small signal response (AM and FM modulations) has been performed for both ILMZ configurations and an ILM. A lower chirp is obtained for the ILMZ compared to the ILM. A high extinction ratio and a low negative effective chirp parameter are predicted at output B of the 2×2 ILMZ, as well as for the π-phase-shifted 2×1 ILMZ