We present the design and characterization of O-band and C-band silicon photonic (SiP) traveling wave Mach-Zehnder modulators (TW-MZM) allowing 220 Gbps/ net rate operation. The designed modulators show over 45 GHz 3-dB E-O bandwidth with a single-segment design. In the O-band, with simple linear feed forward equalization, we transmit net 203 (200) Gbps signal over 2 km (10 km) of single-mode fiber (SMF) below the hard-decision forward error correction (HD-FEC) BER threshold of 3.810-3. With the aid of nonlinear Volterra equalizer and one 2.3Vpp driving signal, we transmit net 225 (216) Gbps PAM8 signals assuming 20% overhead soft-decision FEC with a normalized general mutual information (NGMI) threshold of 0.8798 over 2 km (10 km) of SMF. The C-band design enables net 220 Gbps in B2B and net 215 Gbps over 500 m of SMF above the specified NGMI threshold. These results are the highest reported net rate for SiP MZM in an intensity modulation direct-detection (IM/DD) system, fabricated entirely in a commercial foundry.

As internet traffic demand continues to increase, high-speed electro-optic modulators and high-bandwidth RF components are needed to stretch intensity modulation direct detection (IMDD) systems to their limits. In this study, we experimentally demonstrate the transmission performance using the next generation of digital-to-analog converters (DAC) and high-bandwidth thin-film lithium niobate (TFLN) modulators. In the C-band, we transmit 172 Gbaud PAM6 and 180 Gbaud PAM8 over 120 m of SSMF under the 6.7% overhead hard-decision forward error correction (HD-FEC) and the 20% overhead soft-decision (SD)-FEC thresholds, which respectively correspond to net 400 and 450 Gbps. We also demonstrate the first transmission of net 400 Gbps over 10 km in the O-band (1310 nm) using 172 Gbaud probabilistically shaped (PS)-PAM8 under the 20% SD-FEC BER threshold. Our results indicate that the TFLN platform has the potential to support even higher data rates with the development of high-bandwidth RF components.

Employing our 47 GHz bandwidth silicon photonic (SiP) traveling wave Mach-Zehnder modulator (TW-MZM), we demonstrate the transmission of 134 Gbaud PAM-4 (net 250 Gbps) at a BER below the 6.7% overhead hard-decision forward error correction (HD-FEC) threshold of 3.8 $\times \,\,10^{-3}$ over 2 km of standard single-mode fiber (SSMF) in the O-band with only linear feed- forward equalizer (FFE). With the aid of non-linear pre-distortion and FFE, we transmit 115 Gbaud PAM-8 (net 288 Gbps) and net 305 Gbps PS-PAM-8 above the 19.02% overhead soft-decision FEC with a normalized general mutual information (NGMI) threshold of 0.8798. These results are the highest reported net rates for an all-silicon modulator in an intensity modulation direct-detection (IM/DD) system.

With the exponential growth of internet traffic, driven by the increasing number of connected devices and data-intensive applications, there is an urgent need to address the surging demand for higher capacity in datacenter communications. This paper proposes using O-band single-carrier coherent transmission to achieve 1.6 Tbps for intra-datacenter reach (2-10 km), leveraging the advancements in next-generation DACs and the TFLN platform. To support our proposal, we assess experimentally the gain of employing 256 GSa/s interleaved DACs compared to the current state-of-the-art 128 GSa/s DACs. Additionally, we explore the feasibility of utilizing cost-effective DFB lasers in these short-reach systems. Using the 128 GSa/s DAC and DFB lasers, we transmit 120 Gbaud DP-64QAM over 10 km of SSMF under the 20% overhead SD-FEC threshold, featuring a net rate of 1.2 Tbps. Switching to 256 GSa/s DAC, we achieve net 1.6 Tbps transmission over 10 km with 167 Gbaud DP-64QAM below the 25% SD-FEC BER threshold. We observe that the power penalty of using DFB lasers compared to ECLs is less than 1 dB. Furthermore, this study includes a comprehensive analysis of the power consumption envelope for various candidate configurations targeting 1.6 Tbps operation. The comparison reveals the competitiveness of the O-band single-carrier coherent solution, attributed to its simpler architecture and the inherent features of the TFLN platform. The analysis highlights the potential of the proposed solution as a power-efficient and high-performance option for meeting the demanding requirements of 1.6 Tbps Ethernet.

The escalating datacenter traffic emphasizes the need for high-performance, cost-effective, and energy-efficient optical transceivers. We demonstrate barium titanate (BTO) electro-optic Mach-Zehnder modulators (MZMs) integrated on the silicon photonic platform, surpassing all-silicon counterparts in key metrics: modulation efficiency (VπL = 4.8 Vmm), loss (∼2 dB), and static tuning power (∼100 μW), while maintaining CMOS compatibility. Employing BTO MZMs, we showcase, for the first time, short-reach intensity-modulation and direct-detection (IMDD) transmissions beyond 200 Gbps/λ. In the C-band, over 500 m of standard single-mode fiber (SSMF), we have achieved: (a) a 122 Gbaud PCS-PAM-8 (net 300 Gbps) below the 20% overhead soft-decision forward error correction (SD-FEC) BER threshold of 2.4 × 10 ^-2 , and (b) a 106 Gbaud PAM-4 (net 200 Gbps) below the 6.7% overhead hard-decision (HD) FEC threshold of 3.8 × 10 ^-3 , with a remarkably 9-fJ/bit electrical power dissipation. In the O-band, we transmit (a) a net 200 Gbps over 10-km SSMF below the 5.8% overhead KP4-FEC BER threshold across wavelengths from 1301 nm to 1321 nm, and (b) a net 250 Gbps over 2-km SSMF below the HD-FEC BER threshold ranging from 1291 nm to 1321 nm. Our research highlights BTO MZMs as potent, power-efficient solutions for next-gen transmitters beyond 200 Gbps/λ for intra- and inter-datacenter applications.