Recently, a collaborative team led by Associate Professor Yu Li from Professor Linjie Zhou's group at Shanghai Jiao Tong University's Photonics National Key Laboratory, together with Professor Qunbi Zhuge's team and a Huawei research team, has achieved a breakthrough in high-speed optical interconnects for data centers. They have demonstrated the first 4×256 Gbps silicon-based high-speed transmitter with on-chip adaptive dispersion compensation. This innovation integrates a tunable optical splitter before the silicon Mach-Zehnder modulator (MZM) to adjust the chirp of the modulated signal, enabling adaptive compensation for fiber chromatic dispersion. This addresses a core technical bottleneck limiting the development of high-speed optical communication. The technology provides a promising solution for next-generation data center and high-performance computing optical interconnects, strongly supporting the future deployment of 1.6 Tbps WDM systems, significantly increasing the transmission distance of high-speed modulated signals, and laying a key technological foundation for the global evolution of data centers towards ultra-high speed.
The chip is fabricated based on mature 8-inch Silicon-on-Insulator (SOI) technology, demonstrating excellent potential for large-scale production and industrialization. The related research findings were published in Nature Communications under the title "A 4×256 Gbps silicon transmitter with on-chip adaptive dispersion compensation."
Research Background
Wavelength Division Multiplexing (WDM) technology significantly increases the total bandwidth of optical modules through multi-wavelength parallel transmission. However, as edge wavelengths in WDM systems gradually deviate from the fiber's zero-dispersion wavelength and single-wavelength modulation rates increase rapidly, fiber chromatic dispersion has become a core bottleneck restricting high-speed optical communication development. This challenge is particularly prominent in Coarse Wavelength Division Multiplexing (CWDM) systems: the single-mode fiber dispersion coefficient at the 1271 nm operating wavelength ranges from -2.36 to -4.96 ps/nm/km, severely limiting the transmission distance of modulated signals. In 400GBASE-LR4-6 applications with 100 Gbps per wavelength, the transmission distance for the 1271 nm wavelength signal is only 6 km; in 800GBASE-FR applications with 200 Gbps per wavelength, this distance drops further to 2 km. Facing this bottleneck, the ongoing IEEE 802.3dj specification was forced to abandon the CWDM scheme, instead adopting 8 wavelengths with low dispersion coefficients from the LAN-WDM scheme to achieve 10 km transmission for 200 Gbps per wavelength signals. However, with the explosive growth in communication capacity demand, the limited number of available channels within the low-dispersion wavelength range will be insufficient for future needs. Effectively compensating for dispersion at high-dispersion wavelengths has become a critical technical challenge urgently requiring a solution within the industry.
Innovative Achievement
Fig. 1 Schematic diagram and working principle of the transmitter with dispersion compensation capability
Addressing this core industry pain point, this work pioneeringly proposed and successfully demonstrated a silicon-based MZM transmitter with adaptive dispersion compensation functionality (Fig. 1), providing a revolutionary technical solution to the optical communication transmission bottleneck. By innovatively integrating a tunable optical splitter composed of a 1×2 Mach-Zehnder Interferometer (MZI), the transmitter achieved a breakthrough as the industry's first technology to precisely control the output signal's chirp characteristics simply by adjusting the optical power ratio between the two input arms of the MZM. This enables dynamic generation of pre-chirped modulated signals that perfectly match the fiber's dispersion characteristics. Experimental verification shows that this groundbreaking solution achieves continuous and precise adjustment of the MZM small-signal chirp parameter within the range of [-1, 1], perfectly meeting the stringent requirements for dispersion compensation in O-band WDM systems. More importantly, operating at the 1271 nm high-dispersion wavelength with a fiber dispersion coefficient as high as -3.99 ps/nm/km, the developed silicon photonic transmitter successfully achieved 5 km transmission of 4-channel 256 Gbps PAM-4 signals and 10 km transmission of 4-channel 200 Gbps PAM-4 signals, with bit error rates all below the 6.7% overhead hard-decision forward error correction (HD-FEC) threshold, all without requiring high-power consumption pre-emphasis processing (Fig. 2).
Fig. 2 4-channel 256 Gbps PAM-4 transmission results of the transmitter
The device possesses dispersion compensation capability covering the full wavelength band from 1271 nm to 1340 nm, providing a low-power, highly compatible core optoelectronic device solution for next-generation 1.6 Tbps data center optical interconnects. This not only breaks the transmission distance limitations of traditional CWDM systems but also lays a solid foundation for fully utilizing limited spectral resources and promoting the industrial application of ultra-high-speed optical communication technologies. This technological innovation holds significant value for industry advancement and boasts broad application prospects, providing key technical support for the sustainable development of global data centers and the optical communication industry.
Paper Information
The first author of this work is Shihuan Ran, a 2020 Ph.D. candidate at the Photonics National Key Laboratory, Shanghai Jiao Tong University. Associate Professor Yu Li and Professor Qunbi Zhuge, fixed members of the laboratory, are the corresponding authors. This work received support from projects including the National Natural Science Foundation of China.
Paper link: https://www.nature.com/articles/s41467-025-61408-7
