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As we know, the packaging methods for 100G, 200G, 400G, 800G, and 1600G fiber transceivers are not exactly the same. Why is that?
As the speed increases, PAM4 electrical signal technology, laser quantity (such as 4 λ or 8 λ), and power management become more complex, requiring a new physical architecture to achieve shorter electrical signal transmission paths and more efficient heat dissipation solutions to meet the needs of high-density switches and AI servers, resulting in difficulty in unifying packaging standards.
- The QSFP28 100G SFP module is an early mainstream module with a moderate volume. When starting from 400G/800G, QSFP-DD (Double Density) or OSFP pluggable packaging is used to meet high-density requirements. They cope with high power consumption by increasing the number of channels or increasing the single channel speed, and adding heat sinks at the front end.
- With the development of 800G and higher speeds (1.6T), traditional pluggable transceivers are facing power consumption bottlenecks, and OSFP is more favored in 800G due to better heat dissipation.
- For speeds of 1.6T and higher, the Co Packaged Optics (CPO) technology integrates the optical engine directly with the Switch/GPU, completely breaking the physical limitations of traditional packaging to reduce transmission delay and energy consumption.
Below, we will deeply analyze the core packaging and corresponding interface types of fiber transceivers with different speeds, to facilitate customers in mastering basic knowledge.
100G SFP Module
Mainstream packaging: QSFP28 (most commonly used, 4-channel 25G)
Interface: Duplex LC (for 100G LR4 / 100G CWDM4), MPO-12 (for100G SR4 / 100G PSM4).
Alternative packaging:
- CFP/CFP2/CFP4: Early packaging, large size, now mostly used for long-distance transmission in backbone networks.
- SFP-DD: Less common, mainly used for high-density rack top switches.
200G Transceiver
Mainstream Package: QSFP56 (Mainstream, 4-channel 50G PAM4)
Interface: Duplex LC (for 200G QSFP56 FR4/LR4), MPO-12 (for 200GBASE SR4/DR4).
Alternative packaging: QSFP-DD (dual density packaging)
Interface: MPO-12 or LC. Usually used to maintain physical consistency with 400G ports.
400G Transceiver
Mainstream packaging: QSFP-DD (the most mainstream, backward compatible with QSFP28/56)
interface:
- MPO-12 (APC): Used for QDD 400G DR4 S.
- MPO-16 (APC): Used for 400G SFP SR8.
- Duplex LC: used for 400G FR4 MSA/400G LR4 optics.
- CS interface: Two micro duplex interfaces, commonly used for 2x200G Breakout.
Competitive packaging: OSFP (slightly larger in size, better heat dissipation, favored by big companies such as Google)
Interface: MPO-12/16 or LC.
800G Fiber Transceiver
Mainstream Package 1: OSFP (currently the preferred choice for 800GB, with extremely high heat dissipation efficiency)
Interface:
- MPO-16 (APC): Used for DR8/SR8.
- Duplex LC/2xLC: used for FR4/LR4.
- Duplex CS/2xCS: Used for high-density branch connections.
Mainstream Package 2: QSFP-DD800 (for compatibility with old QSFP ports)
Interface: MPO-16, duplex LC or CS interface.
Summary Table
| Rate | Mainstream Package | Interface type | signal modulation |
| 100G | QSFP28 | LC, MPO-12 | NRZ / PAM4 (single wavelength) |
| 200G | QSFP56 | LC, MPO-12 | PAM4 |
| 400G | QSFP-DD / OSFP | LC, MPO-12, MPO-16, CS | PAM4 |
| 800G | OSFP / QSFP-DD800 | LC, MPO-16, CS | PAM4 |
Key Difference Tips
- Grinding method: Single mode parallel (DR4/DR8/PSM4) must use MPO APC (green) connectors; Multi mode MPO (SR4/SR8) and single mode duplex LC (LR4/FR4) typically use UPC (blue/black).
- MPO specification: The parallel scheme of 400G/800G (SR8/DR8) introduced MPO-16, which is physically incompatible with MPO-12 in the 100G era.