20 × 50 Gb/s electroabsorption-modulated DFB laser array based on the REC technique for data centers

We present and experimentally demonstrate a 20-channel electroabsorption-modulated DFB laser (EML) array, designed as a compact, cost-effective single-chip solution for 1 Tb/s transmitters, targeted for high-performance data center applications, particularly in artificial intelligence (AI) systems. The array utilizes a shared InGaAlAs multiple-quantum-well (MQW) active layer for both the distributed feedback (DFB) lasers and electroabsorption modulators (EAM), enabling a simplified and economically viable monolithic integration. The reconstruction equivalent chirp (REC) technique is used to simplify the grating fabrication and precisely control the wavelength spacing. As a result, the array operates at 20 distinct wavelengths, spaced 100 GHz apart within the L-band. The device demonstrates exceptional single-mode performance, with side-mode suppression ratios (SMSR) exceeding 50 dB and wavelength deviations below 0.15 nm across all 20 channels. The output power reaches 13 mW when the current injected into the semiconductor optical amplifier (SOA) exceeds 140 mA. The EAM bandwidth exceeds 20 GHz for all channels, with static extinction ratios greater than 19 dB. High-quality eye diagrams are obtained at 25 Gb/s non-return-to-zero (NRZ) modulation in back-to-back and 10-km transmission configurations. Additionally, using four-level pulse amplitude modulation (PAM4), the system achieves a per-channel data rate of 50 Gb/s, resulting in a total aggregate data rate exceeding 1 Tb/s across the entire EML array. This EML array's excellent performance and high integration level make it a promising solution for next-generation optical communication systems in data centers, supporting high-speed transmission requirements for AI-driven applications.