512 Gbps/λ dual-polarization thin-film lithium niobate modulators based on an electro-optic equalizer

Driven by the development of AI applications, optical communication systems experience an exponential surge in the demand for high data rates. Thin-film lithium niobate (TFLN) electro-optic (EO) modulators have been extensively studied and show potential for application in next-generation optical communication systems. In this paper, we present a dual-polarization (DP) TFLN EO modulator integrated based on an EO equalizer, fabricated on the lithium-niobate-on-insulator (LNOI) platform. The device consists of an 11-mm-long forward modulation section and a 4.5-mm-long reverse modulation section. It achieves a half-wave voltage (V π ) of 4 V for both Y-polarization (Y-pol) and X-polarization (X-pol), and exhibits an on-chip insertion loss of 2.5 dB for Y-pol and 2.8 dB for X-pol at a wavelength of 1,550 nm. A 3-dB EO bandwidth exceeding 110 GHz with low EO roll-off is achieved for both TE and TM modes. Furthermore, the modulator supports a data transmission rate of 512 Gbit/s in 4-level pulse amplitude modulation (PAM4) format, corresponding to 256 Gbit/s per polarization. This work demonstrates a beyond 400 G/λ solution for implementing a high-speed, and large-bandwidth modulator on a conventional LNOI platform.