A MMI-based ultra-linear high-gain modulator and its performance analysis

An electric optical modulator including a 1 2 multimode interference (MMI) coupler and an integrated Mach–Zehnder Interferometer (MZI) modulator that consists of a microring and a Phase Modulator (PM) is suggested in this paper. Such a modulator can achieve large output RF gain and high linearity performance at the same time. Moreover, due to the application of MMI coupler, traditional direct current (DC) bias circuits can be omitted and the modulator's deterioration caused by the phase error can be decreased a lot, which leads to reduced device complexity and increased device stability. The presented numerical and simulation results confirm the advantages of the newly proposed modulator over conventional modulators (MZI, RAMZI and IMPACC). Further analysis manifests that the proposed modulator has good tolerance in two aspects. Firstly, the modulator has an inherent ability to mitigate the detrimental effects of microring waveguide loss on slope efficiency and linearity by simply adjusting the external RF power split ratio. Secondly, the application of the MMI device increases the modulator's tolerance for the phase deviation caused by some environmental factors. & 2013 Elsevier Ltd. All rights reserved.