Why 400G Optical Modules Are Poised to Transform Data Centers

In 2018 the 100 Gb Ethernet market for data‑center networking was booming, with manufacturers racing to ship mature 100 G products; however, the industry has now moved beyond the 100 G barrier as data‑center bandwidth needs continue to surge.

According to ODCC statistics, by the end of 2017 modular data‑center deployments grew from 300 units in 2013 to 4 500 units, supporting over one million servers, reducing PUE by 0.2‑0.4 and cutting operating costs by 20‑40 %.

To satisfy this demand, the market is focusing on 400 G optical modules, which are expected to lower per‑bit cost. The two dominant 400 G form factors are OSFP and QSFP‑DD, both offering eight 25 GBaud PAM‑4 lanes (8 × 50 Gb/s = 400 Gb/s). OSFP occupies slightly more PCB area, allowing 32 ports per 1U panel, while QSFP‑DD fits 36 ports, offering higher port density and backward compatibility with QSFP and QSFP28.

At the 2018 OFC exhibition, more than ten companies—including Huawei, Finisar, Mellanox, and others—demonstrated 400 G modules, with several already in sample testing and some ready for volume production, forecasting large‑scale deployment in 2019.

Cisco Nexus 400G Switches

Cisco announced four new 400 GbE Nexus models (9316D‑GX, 93600CD‑GX, 3408‑S, 3432D‑S). These switches provide 1‑RU form factors, support up to 32 × 400 GbE ports, and integrate advanced features such as ultra‑fast policies, real‑time packet visibility, intelligent buffering for AI/ML workloads, and seamless integration with ACI, Tetration, and Cisco Network Assurance Engine.

Early field trials are scheduled for December 2018, with full market release expected in the first half of 2019.

Broadcom 400G PAM‑4 PHY (BCM87400)

Broadcom’s 7 nm BCM87400 PHY delivers industry‑leading DSP performance and low power consumption, supporting DR4/FR4/LR4 optical links with 56 Gbaud (112 Gb/s) PAM‑4 across four channels. In 400 G mode it converts eight 53 Gb/s (26‑Gbaud PAM‑4) lanes into four 106 Gb/s (53‑Gbaud PAM‑4) lanes, enabling high‑speed, low‑latency links for cloud and hyperscale data‑centers.

Key features include compliance with IEEE 802.3bs KP4, end‑to‑end FEC bypass, support for both traditional DR/FR modules and emerging silicon‑photonic front‑ends, and a 28‑Gbaud PAM‑4/NRZ SerDes architecture that enhances interoperability with Broadcom ASICs.

Market Outlook

The 400 G module market is expected to expand rapidly as data‑center operators seek higher bandwidth at lower cost. While QSFP‑DD offers higher port density, its smaller footprint imposes stricter design constraints that may increase module cost. Both form factors currently serve diverse customer needs, and the first to achieve large‑scale deployment will likely capture a significant market advantage.

Overall, the convergence of advanced 400 G optical modules, Cisco’s high‑performance Nexus switches, and Broadcom’s cutting‑edge PHY chips signals a pivotal shift toward the next generation of data‑center networking.