400G optical transport scales data center interconnects in China
China’s rapidly growing cloud, AI, and e-commerce ecosystems are pushing backbone links between data centers to new limits. 400G optical transport has emerged as a practical way to expand capacity, improve spectral efficiency, and streamline operations across metro and regional networks while preparing for future traffic growth.
Behind every request to a cloud app lies an optical path carrying massive volumes of data between facilities. In China, that path increasingly runs over 400G optical transport, which delivers 400 gigabits per second per wavelength across dense wavelength-division multiplexing (DWDM) systems. For data center interconnects (DCI), 400G helps operators increase bandwidth per fiber, reduce cost per bit, and automate provisioning across metro rings and regional corridors.
Tech gadgets and the 400G backbone
Consumers interact with tech gadgets daily, from smartphones to wearables, but the responsiveness they experience depends on fast east–west traffic between data centers. 400G coherent optics make this possible by packing more bits into each symbol and improving spectral efficiency. For short to medium DCI spans, 400G ZR and ZR+ pluggables in QSFP‑DD or OSFP form factors slot directly into routers, eliminating separate transponder shelves and cutting power usage while keeping latency low.
Digital devices and data flows
Digital devices generate a continuous stream of uploads, recommendations, and AI inference requests. Within China’s digital economy—spanning fintech, streaming, and industrial IoT—this translates into high burstiness and strict jitter targets. 400G transport addresses these needs with flexible modulation (for example, shifting between 16QAM and QPSK over longer distances), forward error correction, and intelligent restoration that reroutes wavelengths around fiber cuts. The result is more predictable performance during peak hours and faster recovery from faults.
Online services driving capacity
Online services—from video platforms to enterprise SaaS—are major drivers of DCI growth. Many operators are converging IP and optical layers using IP‑over‑DWDM, where routers host 400G coherent pluggables and connect to open line systems. This reduces equipment layers and simplifies scaling in metro clusters around Beijing–Tianjin–Hebei, Yangtze River Delta, and Greater Bay Area. For longer regional routes linking inland computing hubs, 400G ZR+ or chassis‑based coherent engines extend reach while maintaining high channel counts via C‑ and C+L‑band ROADMs.
Electronic accessories: optics and cabling
While “electronic accessories” often suggests consumer add‑ons, in the DCI world it points to pluggable optics, patch panels, and cabling that determine practical throughput. Choosing between QSFP‑DD and OSFP, qualifying 400G DACs and AOCs inside facilities, and standardizing on single‑mode fiber with low‑loss connectors all affect usable capacity. OpenZR+ interoperable modules allow multi‑vendor deployments, and strict optical budgets—accounting for splices, connectors, and ROADMs—ensure 400G channels stay within margin across diverse fiber routes.
Internet connectivity across regions
China’s network topology is expanding beyond coastal data center clusters to inland provinces, supporting national computing initiatives that balance resources across regions. This shift increases the importance of resilient DCI corridors with diverse fiber paths and automated provisioning. With 400G, operators can scale wavelengths quickly, add channels without new fiber builds, and use telemetry to optimize spectrum. For local services in your area, consistent latency across metro and regional hops supports smoother app experiences during national shopping festivals and live events.
Providers and offerings in China
A robust vendor and carrier ecosystem supports 400G optical transport for DCI. Equipment vendors supply coherent optics, line systems, and automation software, while carriers deliver managed wavelength services and fiber access for enterprises and cloud providers.
| Provider Name | Services Offered | Key Features/Benefits |
|---|---|---|
| China Telecom | Managed wavelength services, dark fiber in select metros, enterprise DCI | Wide national footprint, diverse routing options, SLAs for latency and availability |
| China Mobile | Metro/regional DCI services, wholesale capacity | High‑capacity corridors between major cities, rapid scaling during traffic peaks |
| China Unicom | Carrier wavelength and Ethernet private lines | Cross‑regional connectivity, integration with enterprise access services |
| Huawei | 400G optical transport platforms and coherent pluggables | IP‑over‑DWDM, ROADM automation, C/C+L‑band expansion, telemetry and SDN control |
| ZTE | 400G DWDM systems and ZR/ZR+ solutions | Power‑efficient coherent engines, metro‑to‑regional reach, multi‑layer optimization |
| Ciena | 400G coherent optics and open line systems | Interoperability with OpenZR+, advanced performance monitoring, automation toolsets |
| Nokia | 400G transport platforms and network controllers | Multi‑vendor integration, flexible modulation, path computation and restoration |
| Infinera | Coherent engines and line systems supporting 400G | High spectral efficiency, compact platforms for DCI, analytics‑driven capacity planning |
Design tips for reliable 400G DCI
- Validate optical budgets end‑to‑end, including connectors and ROADMs, before turning up new wavelengths.
- Use diverse physical routes for primary and backup paths to mitigate conduit‑level risks.
- Consider IP‑over‑DWDM with 400G pluggables to simplify architecture in metro rings; use chassis‑based transponders where spans or filters demand higher OSNR margins.
- Standardize on coherent modules that support open management models and streaming telemetry for proactive maintenance.
Operations, automation, and sustainability
Operations teams benefit from controller‑based planning and real‑time telemetry that track error vectors, OSNR, and polarization effects. Closed‑loop automation can preemptively adjust launch power or modulation when margins tighten. From a sustainability viewpoint, 400G increases bits per joule, allowing more workload per rack and reducing the need for new fiber builds. Combined with C+L‑band expansion and higher‑order modulation, networks can defer trenching while meeting the performance goals of cloud, AI, and content delivery platforms.
Looking ahead to 800G
Many operators are evaluating a mix of 400G for mainstream DCI and higher‑rate wavelengths for backbone upgrades. The current 400G wave creates a stable foundation—mature optics, interoperable standards, and proven automation—so capacity can be added incrementally as demand grows. In the near term, expanding 400G channels across metro clusters and key regional routes will remain a practical path to keep applications responsive for users nationwide.
In summary, 400G optical transport gives data center operators in China a scalable, power‑efficient way to expand interconnect capacity. By combining coherent pluggables, open line systems, and smarter automation, networks can handle surges from online services while maintaining predictable performance for the devices people rely on every day.