DoGain Unveils 100G PAM4 CWDM EML Chips and COC Devices to Fully Support 400G-FR4/800G-FR8 Optical Interconnections in Data Centers

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As the computing power scale of AI large-model training clusters and supercomputing centers continues to expand, internal data traffic within data centers is rising exponentially, and optical interconnection architectures are rapidly evolving from 400G toward 800G and 1.6T. Industry forecasts indicate that 800G optical modules will remain the mainstream of the market in 2026. Among them, 400G-FR4 and 800G-FR8 optical modules have become the primary choice for data center interconnections, thanks to outstanding features such as multi-wavelength multiplexing over a single fiber pair and a 2-km transmission reach. Nevertheless, as the per-channel rate jumps to 100G PAM4, conventional light source solutions face severe challenges in bandwidth, extinction ratio, modulation linearity and temperature control stability. Domestic mass production of high-end EML chips has thus become an urgent priority.

To address these critical industry pain points, DoGain has officially launched its 100G PAM4 high-speed EML chips (1271/1291/1311/1331 nm) and supporting COC devices. Leveraging the strengths of its self-owned full-stack IDM platform, the company has achieved comprehensive breakthroughs in bandwidth, extinction ratio, linear modulation and spectral stability. It delivers highly reliable, high-efficiency and cost-effective light source solutions for high-speed optical interconnection applications of 400G-FR4 and 800G-FR8 in AI data centers.

Technology Breakthrough:

Self-developed High-Speed Architecture Delivers Comprehensive Performance Leap

The newly launched 100G PAM4 CWDM EML chip by DoGain monolithically integrates a high-performance DFB laser and an electro-absorption modulator (EAM) on a single die. Equipped with a proprietary high-speed modulation architecture and advanced epitaxial design, it fundamentally resolves industry bottlenecks of conventional DFB solutions at high bit rates, such as insufficient bandwidth, degraded extinction ratio and modulation nonlinearity.

The product achieves a modulation bandwidth exceeding 40 GHz with ample bandwidth margin, fully satisfying the requirements of 100G PAM4 high-speed modulation and reserving sufficient headroom for system-level signal integrity. Benefiting from its external modulation feature, the EML chip effectively suppresses the chirp effect produced by laser chips under high-speed modulation, maintaining excellent signal quality over long-distance transmission.

In terms of extinction ratio performance, the chip delivers an extinction ratio above 8 dB across the full operating temperature range. It sustains high extinction ratio under varied temperature conditions and enables clear, well-opened PAM4 signal eye diagrams. This guarantees signal transmission quality and system link margin for 400G-FR4/800G-FR8 modules working in multi-channel parallel operation.

EA Linear Absorption

Enabling Robust PAM4 Modulation

To meet the stringent linearity requirements imposed on modulators by the PAM4 high-order modulation format, the electro-absorption modulator (EAM) integrated within DoGain’s EML chip achieves excellent EA linear absorption characteristics, thanks to its proprietary quantum-well structure and precision doping design. The EAM modulates optical signals by varying its light absorption capacity, and its linearity directly governs the amplitude uniformity among the four PAM4 levels as well as eye diagram quality. With proprietary optimized design, the chip demonstrates outstanding linear response and low nonlinear distortion under PAM4 modulation. It enables high-speed modulation of 100 Gbps per-channel PAM4 signals and provides a solid light-source foundation for 400G-FR4 (4×100G) and 800G-FR8 (8×100G) architectures.

High-Performance Grating

Single-Mode with Spectrum Stability Across Full Temperature Range

Wavelength accuracy and spectral stability are the lifeline of multi-wavelength multiplexing systems. Equipped with a proprietary high-performance distributed feedback grating, DoGain’s EML chip adopts precise grating design and temperature compensation mechanisms to ensure accurate wavelength locking on the CWDM4 wavelength grid (1271/1291/1311/1331 nm). The product delivers stable single-mode spectral output under varying temperature conditions with excellent side-mode suppression ratio. It effectively mitigates wavelength drift and mode hopping risks induced by temperature changes, and fundamentally guarantees the crosstalk isolation of multi-wavelength channels and overall system stability within 400G-FR4/800G-FR8 modules.

System-level Supporting Components: Delivery of Highly Reliable COC Devices

To match the high-performance merits of the chip and meet mass-production requirements of downstream customers, DoGain has rolled out supporting COC (Chip on Carrier) devices. Adopting dedicated high-thermal-conductivity heat sink materials together with advanced eutectic packaging technology, the devices feature outstanding heat dissipation performance, which fully guarantees long-term operational stability under high-power and high-bit-rate working conditions. Meanwhile, the products undergo rigorous COC-level performance screening with high parameter consistency and strong reliability. No secondary tuning or optimization is required on the customer side. Supporting plug-and-play and fast assembly, they are fully compatible with the full series of silicon photonic transceivers and EML TOSA solutions for 400G-FR4 and 800G-FR8.

Key Product Benefits

Ultra-high bandwidth margin: Modulation bandwidth >40 GHz, fully meeting 100G PAM4 modulation requirements and reserving sufficient headroom for system-level signal integrity.
Excellent extinction ratio across full temperature range: Extinction ratio >8 dB over the entire operating temperature range, maintaining high-quality PAM4 signal eye diagrams under varied temperature conditions.
EA linear absorption for robust PAM4 modulation: Outstanding linear response and low nonlinear distortion, providing core assurance for amplitude uniformity of the four PAM4 levels.
High-performance grating for stable single-mode spectrum: Proprietary high-performance Bragg grating enables stable single-mode spectral output at different temperatures.
High-reliability mass production delivery: Advanced eutectic packaging plus high-efficiency heat sink design, together with standardized performance screening, deliver superior device consistency and stability. The fully self-controllable IDM workflow ensures rapid product delivery.