Quadrature amplitude modulation (QAM) using binary-driven coupling-modulated rings

• We propose and fully analyze a compact structure for DAC-free pure optical QAM modulation.
• The proposed structure is the first ring resonator-based QAM modulator reported.
• The device consists of two segmented add-drop MZIARM in an IQ scheme.
• We have included the loss in MZI arms in our analysis of phase and amplitude modulation using MZIARM.
• We show that the unbalanced loss results in a phase error.
• The output level linearity is also studied for both QAM-16 and QAM-64.
• RF segment lengths and number were optimized.

We propose and fully analyze a compact structure for DAC-free pure optical QAM modulation. The proposed structure is the first ring resonator-based DAC-free QAM modulator reported in the literature, to the best of our knowledge. The device consists of two segmented add-drop Mach Zehnder interferometer-assisted ring modulators (MZIARM) in an IQ configuration. The proposed architecture is investigated based on the parameters from SOI technology where various key design considerations are discussed. We have included the loss in the MZI arms in our analysis of phase and amplitude modulation using MZIARM for the first time and show that the imbalanced loss results in a phase error. The output level linearity is also studied for both QAM-16 and QAM-64 not only based on optimizing RF segment lengths but also by optimizing the number of segments. In QAM-16, linearity among levels is achievable with two segments while in QAM-64 an additional segment may be required.