As global backbone networks and hyperscale data centers continue to scale, 400G has become the inevitable direction for next-generation upgrades and new infrastructure deployments. This article introduces the fundamentals, standards, and market trends surrounding 400G optical modules, a core technology for modern AI and cloud networks.
π What Is a 400G Optical Module? #
A 400G optical module performs photoelectric conversion:
- Electrical β Optical at the transmitter
- Optical β Electrical at the receiver
With a 400 Gbps transmission rate, these modules support industry evolution from 100M β 1G β 25G β 40G β 100G β 400G β 1T. They form the backbone of high-throughput data center networks and AI clusters.
This raises a key question:
What standards and packaging types define the 400G ecosystem?
Below are the six mainstream 400G optical module standards.
π¦ Major 400G Optical Module Standards & Form Factors #
1. OSFP #
OSFP (Octal Small Formfactor Pluggable) is a new interface standard not backward-compatible with existing QSFP/XFP modules.
- Size: 100.4 Γ 22.58 Γ 13 mmΒ³
- Slightly larger than QSFP-DD
- Dual-side electrical interface pins
2. QSFP-DD #
QSFP-DD (Quad Small Form Factor Pluggable β Double Density) extends the classic QSFP interface from 4 lanes β 8 lanes, enabling 400G.
Key advantage: Backward-compatible with QSFP/QSFP28 modules.
3. CFP8 #
CFP8 scales the older CFP4 standard with 8 channels, requiring:
- 16 Γ 25G lasers
- Larger module size: 40 Γ 102 Γ 9.5 mmΒ³
- Higher cost compared to QSFP-DD/OSFP
4. CWDM8 #
An extension of CWDM4, using:
- 50G per wavelength
- 8 wavelengths (adds 1351/1371/1391/1411nm)
- Wider wavelength spacing and stricter Mux/DeMux requirements
Max input power: 8.5 dBm
5. CDFP #
An early 400G form factor using:
- 16 channels Γ 25G
- Large physical size due to high lane count
6. COBO #
COBO (Consortium for On-Board Optics) mounts optics directly onto the PCB, offering:
- Excellent thermal performance
- Very compact size
However, no hot-swap capability, making field service more difficult.
ποΈ Which Standards Will Dominate? #
At OFC 2018, OSFP and QSFP-DD emerged as the strongest candidates. Their final adoption depends largely on future cloud network architecture decisions by hyperscale operators.
π― What Is the Purpose of a 400G Optical Module? #
400G modules are engineered to:
- Increase data throughput
- Maximize port density
- Reduce per-bit energy cost
- Enable AI-scale data center fabrics
Future trends include:
- Wider gain
- Lower noise
- Higher integration
- Optical-electronic miniaturization
𧩠How Many Chips Are Used in a 400G Module? #
Although a single optical chip is used, the cost is high:
- 10G/25G: chip cost β 30%
- 40G/100G: chip cost β 50%
- 400G: chip cost β 70%
This cost scaling reflects the complexity of high-speed coherent optics, DSP packaging, and thermal design.
π How Do 400G Modules Differ from 10G, 25G, and 40G? #
As network demands grow, 400G introduces a new architecture era:
- Moves from simple single-carrier modulation
- Shifts toward polarization multiplexing + multi-carrier coherent detection
- Relies heavily on ADC/DSP, photonic integration, and parallel optics
Standardization of 400G Ethernet further accelerates optical parallelization and advances silicon photonics technologies.
π What Is the Market Value of 400G Optical Modules? #
With 100G products mature, the industry is transitioning to 400G because:
- Hyperscale data centers require massive bandwidth increases
- 400G reduces cost per bit
- 5G/AI/cloud workloads push higher-speed backbone upgrades
- 400G modules are already in mass production with strong commercial momentum
400G is now the mainstream growth engine of next-generation optical communication.