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400G QSFP-DD has become one of the most popular form factors in the next-generation network. And different types of modules have appeared in the 400G optical transceiver market. What are 400G QSFP-DD transceiver types? What fiber cables could be used with these 400G optical modules? What about the answers to frequently asked questions about 400G QSFP-DD? This post will illustrate them thoroughly.
400G QSFP-DD Transceiver Types
There are several main 400G QSFP-DD transceiver types in the market, such as 400G QSFP-DD SR8, 400G QSFP-DD DR4, 400G QSFP-DD FR4, 400G QSFP-DD LR4, 400G QSFP-DD LR8, etc. The following table will give an introduction to them respectively according to the two transmission types (over multimode fiber and single-mode fiber) they support.
| Transmission Type | QSFP-DD Product Description | Reach | Optical Connector | Wavelength | Optical Modulation | Protocol |
|---|---|---|---|---|---|---|
| Multimode fiber | 400G QSFP-DD SR8 |
up to 100m over OM4 up to 70m over OM3 |
MTP/MPO-16 | 850nm | 50G PAM4 |
IEEE P802.3c IEEE 802.3cd |
| Single-mode fiber | 400G QSFP-DD DR4 | up to 500m over parallel SMF | MTP/MPO-12 | 1310nm | 100G PAM4 | IEEE 802.3bs |
| 400G QSFP-DD XDR4/DR4+ | up to 2km over parallel SMF | MTP/MPO-12 | 1310nm | 100G PAM4 | / | |
| 400G QSFP-DD FR4 | up to 2km over duplex SMF | LC | CWDM4 wavelength | 100G PAM4 | 100Glambda MSA | |
| 400G QSFP-DD 2FR4 | up to 2km over duplex SMF | CS | CWDM4 wavelength | 50G PAM4 | IEEE 802.3bs | |
| 400G QSFP-DD LR4 | up to 10km over duplex SMF | LC | CWDM4 wavelength | 100G PAM4 | 100Glambda MSA | |
| 400G QSFP-DD LR8 | up to 10km over duplex SMF | LC | 1310nm | 50G PAM4 | IEEE 802.3bs |
Fiber Connections for 400G QSFP-DD Transceivers
QSFP-DD SR8
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A 400G QSFP-DD SR8 can be connected with another QSFP-DD SR8 over a MTP-16 cable. This is the most popular connection using an MTP-16 cable to connect two 400G QSFP-DD SR8 transceivers directly.
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QSFP-DD SR8 to 2*200G SR4 over MTP-16 to 2*MTP-8 breakout cable.
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QSFP-DD SR8 to 8*50G SFP over MPO-16 to 8*LC duplex fiber cables.
QSFP-DD DR4
QSFP-DD DR4 to 4* 100G DR over MPO-12 to 4*LC duplex breakout cable.
400G QSFP-DD XDR4/DR4+
The 400G optical module has an extended version, namely 400G QSFP-DD XDR4/DR4+. Connect 400G QSFP-DD XDR4 module with 4 QSFP-DD 100G FR modules over a MPO-12 to 4 Duplex LC cable.
QSFP-DD FR4
QSFP-DD FR4 to QSFP-DD FR4 over duplex LC cable.
QSFP-DD 2FR4
QSFP-DD 2FR4 to 2*200G FR4 over 2*CS to 2*LC duplex breakout cable.
400G QSFP-DD Transceivers: Q&A
Q: What does "SR8", "DR4", "XDR4", "FR4", "LR4", and "LR8" mean?
A: "SR" refers to short range, and "8" implies there are 8 optical channels. "DR" refers to 500m reach using single-mode fiber, and "4" implies there are 4 optical channels. "XDR4" is short for "eXtended reach DR4". And "LR" refers to 10km reach using single-mode fiber.
Q: Can I plug a QSFP-DD transceiver module into an OSFP port?
A: No. QSFP-DD and OSFP are totally different form factors. For more information about OSFP transceivers, you can refer to 400G OSFP Transceiver Types Overview. You can use only one kind of form factor in the corresponding system. Eg, if you have a QSFP-DD system, QSFP-DD transceivers and cables must be used.
Q: Can I plug a 100G QSFP28 module into a QSFP-DD port?
A: Yes. A QSFP28 module can be inserted into a QSFP-DD port (without a mechanical adapter). When using a QSFP28 module in a QSFP-DD port, the QSFP-DD port must be configured for a data rate of 100G instead of 400G.
Q: What other breakout options are possible apart from using QSFP-DD modules mentioned above?
A: QSFP-DD 400G DACs & AOCs are possible for breakout 400G connections. See 400G Direct Attach Cables (DAC & AOC) Overview for more information about 400G DACs & AOCs.