Evolution and Trends of 25G/50G/100G/400G Optical Modules in Data Center and Transport Networks

25G optical modules are becoming the mainstream front‑haul solution. Two main chip approaches exist: native 25G chips, which offer higher reliability and stability but require advanced manufacturing and are largely sourced overseas, and 10G chips that are over‑clocked to 25G, benefiting from a mature domestic supply chain and lower cost.

The 25G chip solution remains the optimal choice, with production capacity expected to scale significantly in 2020. The key difference between the over‑clock and native 25G solutions lies in the transmitter: the native approach uses a dedicated 25G chip, while the over‑clock method employs a 10G laser driver combined with a 25G LD driver.

In 2019, insufficient 25G chip capacity and the cost advantage of 10G chips led to widespread adoption of the over‑clock solution. As overseas manufacturers shift production toward 25G chips, domestic firms such as Guangxun Technology have achieved mass production of 25G DBF chips, anticipating increased capacity and reduced costs in 2020.

Transport networks are upgrading: metro networks are moving from 10G/40G to 100G, while backbone networks transition from 100G to 400G. The rollout of 5G, especially SA architecture with network slicing, requires synchronized upgrades of the transport layer.

Backbone, provincial, and metro networks have different requirements. Backbone and provincial networks favor high‑capacity, long‑distance solutions like OTN, whereas metro networks are divided into core, aggregation, and access layers, each using distinct port speeds and corresponding optical modules.

With rising mobile communication speeds, transport layers are evolving: access layers upgrade from 10G to 25G/50G, aggregation layers from 40G/100G to 50G/100G, and core layers from 100G to 200G, while wavelength‑division multiplexing systems become more compact.

Large‑scale data‑center construction is driving the industry into the 400G era. Cloud data centers demand higher speeds than traditional centers, shifting from 1G/10G modules to 40G/100G/400G modules. The increase in east‑west traffic within data centers amplifies the need for high‑speed transceivers.

Data‑center interconnect trends show server‑to‑TOR links moving from 10G/25G toward 50G/100G, and leaf‑to‑spine or inter‑data‑center links transitioning from 40G/100G to 400G.

For 400G packaging, QSFP‑DD and OSFP are emerging as the dominant form factors, offering advantages in size, thermal performance, power consumption, backward compatibility, and bandwidth compared to CDFP and CFP8.

Many vendors have adopted QSFP‑DD for 400G production, making it the market‑preferred solution, while some also offer OSFP and CFP8 variants.

Optical modules, as electro‑optical conversion components, are widely used in broadband, telecom, data‑center, security surveillance, and smart‑grid applications. Data‑center connectivity can be categorized into three types: data‑center‑to‑user, data‑center interconnect, and internal data‑center communication.

The increasing scale and flattening of data centers demand higher‑capacity, higher‑speed optical modules. Multimode fiber is being replaced by single‑mode solutions such as PSM4 and CWDM4 for short‑reach, while CWCM modules address longer‑reach requirements, often combined with external wavelength‑division multiplexers to maximize fiber utilization.

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