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Answer: The 400G DR4 transceiver module utilizes a MPO 12 APC fiber interface (or MTP 12 APC).
Although the 400G DR4 standard requires only 8 fiber cores (4 fiber for transmission + 4 fiber for reception), it employs a standard MPO 12 connector for its physical packaging, with a standard transmission distance of 500 meters.
400G DR4 Specifications
Interface Type: MPO-12 (APC) or MTP-12 (APC)
Important Note: DR4 utilizes single-mode parallel transmission; therefore, connectors featuring an APC (green, 8°angled) polish are mandatory to minimize return loss, it is a critical requirement in high-speed transmissions employing PAM4 modulation. The incorrect use of UPC (blue, flat) connectors—commonly found in multi-mode applications—will result in severe signal reflections.
Fiber Utilization:
- Of the 12 fiber ports, only the outermost 8 positions are utilized (the 4 on the left for Tx, and the 4 on the right for Rx).
- The 4 central positions remain idle.
Why not use MPO-8?
Although only 8 fibers are actually utilized, industry standards—such as IEEE 802.3bs—defined the 400G DR4 interface by adopting the mature MPO-12 physical housing established during the 100G SR4 era. Consequently, MPO MTP patch cords marketed as “MPO-8” essentially employ the MPO-12 housing as well; they simply contain only 8 internal optical fibers.
Connection Recommendations
Direct Connection (400G-400G): Use a single mode 12 fiber MTP Cable (APC).
1-to-4 (400G-4x100G): Use a single-mode branch patch cord from MPO-12 (APC) to 4x duplex LC (UPC).
- 400G end: Connect to the MPO-12 (APC) port.
- 100G end: Connect to the duplex LC port of four 100G DR1 modules.
Difference, 400G FR4 vs DR4
The primary advantages of the 400G DR4 over the 400G FR4 lie in network flexibility (specifically, Breakout capability) and module cost, making it particularly well-suited for short-distance interconnects within data centers.
Breakout Connection Capability:
- The DR4 employs a 4-lane parallel design (100G per lane); via an MPO-12 interface, it can be easily split into four distinct 100G ports (connecting to 100G DR1/FR1 modules).
- The FR4 utilizes Coarse Wavelength Division Multiplexing (CWDM) technology to combine four distinct wavelengths onto a single pair of fibers; consequently, it cannot support direct physical-layer breakout connections.
Lower Module Cost:
- The internal structure of the 400G DR4 optics is relatively simple; since all four optical signals operate at the same 1310nm wavelength, it does not require complex Wavelength Division Multiplexing/Demultiplexing (Mux/Demux) components. As a result, the manufacturing cost per 400G DR4 transceiver module is typically lower than that of the 400G FR4 transceiver.
Low-Latency Performance:
- Since 400G DR4 MPO utilizes parallel transmission, its internal optical path design is more direct. In contrast, 400G FR4 transceiver typically requires the multiplexing and demultiplexing of multiple wavelengths; furthermore, certain implementation schemes (such as early Gearbox designs converting 8 electrical lanes to 4 optical lanes) may introduce additional DSP latency.
Silicon Photonics Integration:
- 400G DR4 QSFP DD is highly suitable for the adoption of silicon photonics integration technology, which helps to further reduce power consumption and improve manufacturing yields in high-volume production.
| Item | 400G DR4 | 400G FR4 |
| Optical Interface | MPO-12 (APC) | Duplex LC |
| Transmission Distance | 500 meter | 2km |
| Fiber Requirements | 8 core（4 transit 4 receive） | 2 core（1 transmit 1 receive） |
| Breakout | Support (4x100G) | Not supported |
| Key Applications | Interconnection of Switches and Servers / Existing 100G Equipment | Long-Distance Backbone Interconnection Between Switche |
What DR4-architecture fiber optic products can Yingda provide?
The DR4 architecture (parallel 4-channel, single-mode, 500m) encompasses a complete ecosystem of products, ranging from fiber to ethernet transceiver and MPO optical cable to network equipment. Yingda offers the following products to assist you in building DR4-architecture systems.
400G DR4 Transceiver
It adopt QSFP-DD or OSFP packaging, based on four 100G PAM4 signals.
800G DR4 Transceiver
It typically utilizes an OSFP form factor and employs four lanes of 200G PAM4 signals. Some designs are configured as “2xDR4” to provide higher port density.
1.6T DR4 Transceiver
Single-lane speeds leap to 400G, specifically designed for next-generation AI computing centers.
MPO Breakout Cable
For example, an 12 Fiber MPO to 4LC duplex patch cord is used to split a 400G DR4 port into four 100G DR1 connections.
FHD MTP Patch Panel
Specifically designed for MPO architectures, for use in structured cabling between data center racks.
12 Fiber MTP MTP Cable
The standard connection cables for DR4 modules must utilize APC (Angled Physical Contact) polishing to suppress return loss.
Conclusion
400G DR4 transceivers primarily utilize MPO 12 APC single mode interfaces.
- If you need to split a single 400G port into four 100G ports to ensure compatibility with existing equipment, the 400G DR4 breakout cable is your only option.
- However, if your goal is to conserve fiber resources for long-distance (500m–2km) direct connections, the 400G FR4 optics offers distinct advantages.
Should you require any other MPO-related patch cords or MTP patch panels, contact us for quotaion sheet.
