Dynamic analysis of OOK modulators using eye diagrams to assess data rate and output matching

Official URL: https://dx.doi.org/10.1109/SMACD65553.2025.11092237

This paper presents a high-speed On-Off Keying (OOK) modulator in 65 nm CMOS, evaluated at data rates up to 50 Gbps. Eye diagrams are generated via a Hilbert transform from transient simulation data, enabling direct measurement of rise/fall times and eye openings at the modulator output. For 50 Gbps operation, the well-matched design achieves a rise time of 13.59 ps and a fall time of 17.95 ps, whereas the loosely matched design exhibits 25.34 ps and 28.00 ps, respectively. To assess the impact of communication-chain bandwidth, band-pass filters with 200 GHz, 150 GHz, and 100 GHz bandwidths - chosen based on covering the main lobe and varying extents of the side lobes - were introduced. As the bandwidth decreases, rise times for both matching conditions converge, reaching 35.47 ps (well-matched) and 34.72 ps (loosely-matched) at 100 GHz, suggesting bandwidth constraints dominate over matching. However, the fall time difference persists, with 21.44 ps and 24.24 ps at 100 GHz for well-matched and loosely matched cases, respectively, underscoring the importance of output matching. Additionally, the normalized eye height narrows more significantly in the loosely matched case.