What Factors Should be Considered When Choosing the Right 400G Transceiver for Multimode Fiber? What are the Most Common Applications for Each Transceiver Type?
Selecting the right 400G transceiver for multimode fiber involves many factors. Here are some of the key considerations:
Distance: The range of operations for each type of transceiver varies. Before choosing a transceiver, you should know the exact distance between the systems you plan to connect. Short-range transceivers are typically used for distances up to 70m, while long-range variants can cover distances above 2km.
Power Consumption: Power usage can vary substantially from one transceiver type to another.聽 Higher capacity transceivers often use more power. Ideally, you should aim for a transceiver that offers the required data rate at the lowest possible power consumption.
Cost: Pricing can vary significantly between different transceivers. The overall cost should be evaluated in the context of your specific networking needs and budgetary constraints.
Compatibility: Not all transceivers will be compatible with your switches, routers, or other network devices. Be sure to confirm that the transceiver you choose works with your existing hardware.
Interconnection: Consider how different transceivers suit your interconnection environments. Transceivers come in different form factors such as QSFP-DD, OSFP, CFP2, CFP8, or COBO, and each has its own specifications for things like power consumption, size, and interface.
Reliability and Durability: The lifespan and durability of the transceivers also come into play. High-quality transceivers are built to last, reducing the need for replacements and maintenance.
The key features and common applications of each of these transceivers are described below.
1.The OSFP-400G-SR8 / SR8-C and QDD-400G-SR8 / SR8-C
The 400G-SR8 was the first 400G MMF transceiver available and has been deployed for point-to-point 400GE applications, such as leaf-to-spine connectivity, illustrated below.
While the 400G-SR8 provides cost-effective 400GE connectivity over MMF, it requires 16 fibers per transceiver and uses an MPO-16 APC fiber connector. Most 40G and 100G parallel MMF optics (such as the 40G-SR4 and 100G-SR4) use MPO-12 UPC fiber connectors. MPO-16 to 2x MPO-12 patch cables are required to use a 400G-SR8/SR8-C transceiver over an MPO-12 UPC-based fiber plant.
Another key application for 400G-SR8 transceivers is optical breakout into 2x 200G-SR4 links, enabling TOR-to-host connectivity where 200G to the host is required, as illustrated below.
The 400G-SR8-C transceiver has the same features as the 400G-SR8, with the added ability to breakout into 8x 50G-SR or 8x 25G-SR optical links. It can therefore be used in applications that require high-density 50G or 25G breakouts 鈥?as illustrated below.
- The OSFP-400G-SRBD and QDD-400G-SRBD, or 鈥?00G-BIDI鈥漷ransceivers.
400G-BIDI transceivers use the widely deployed MPO-12 UPC connector for parallel multimode fiber. This allows existing 40G or 100G links that use 40G-SR4 or 100G-SR4 QSFP optics to be upgraded to 400GE with no change to the fiber plant, as illustrated below:
When configured for 400GE operation, the 400G-BIDI transceiver is compliant with the IEEE 400GBASESR4.2 specification for 400GE over 4 pairs of MMF.
Arista鈥檚 400G-BIDI transceivers are also capable of breaking out into 4x 100GE links and can be configured (via EOS) to interoperate either with the widely deployed base of 100G-BIDI (100G-SRBD) transceivers, or newer 100G-SR1.2 transceivers, as indicated below.
In summary, Arista鈥檚 400G-BIDI transceiver is software configurable to operate in any one of three operating modes:
i) 400G-SR4.2 for point-to-point 400GE links
ii) 4x 100G-BIDI for breakout and interop with 4x 100G-BIDI (100G-SRBD) transceivers
iii) 4x 100G-SR1.2 for breakout and interop with 4x 100G-SR1.2 transceivers
FAQS
Q: 400G QSFP-DD vs 400G OSFP/CFP8: What are the differences?
A: The table below includes detailed comparisons for the three main form factors of 400G transceivers.
| 400G Transceiver | 400G QSFP-DD | 400G OSFP | CFP8 |
|---|---|---|---|
| Application Scenario | Data center | Data center & telecom | Telecom |
| Size | 18.35mm× 89.4mm× 8.5mm | 22.58mm× 107.8mm× 13mm | 40mm× 102mm× 9.5mm |
| Max Power Consumption | 12W | 15W | 24W |
| Backward Compatibility with QSFP28 | Yes | Through adapter | No |
| Electrical signaling (Gbps) | 8× 50G | ||
| Switch Port Density (1RU) | 36 | 36 | 16 |
| Media Type | MMF & SMF | ||
| Hot Pluggable | Yes | ||
| Thermal Management | Indirect | Direct | Indirect |
| Support 800G | No | Yes | No |
Q: How does the QSFP+ to SFP+ fiber convertor allow 4x 10G?
A: To enable 4x 10G connectivity, a QSFP+ to SFP+ fiber converter utilizes a breakout cable. This cable splits the 40G channel provided by the QSFP+ transceiver into four individual 10G channels, each connected to an SFP+ transceiver. Essentially, the converter breaks down the high-speed 40G signal into four separate 10G signals, allowing each SFP+ port to transmit data at 10G speeds. This configuration is beneficial for scenarios where equipment with SFP+ interfaces needs to communicate with a device equipped with a QSFP+ port, providing flexibility and compatibility in networking setups.
Q: What does “SR8”, “DR4”, “XDR4”, “FR4”, and “LR4” 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 an OSFP transceiver module into a QSFP-DD port?
A: No. QSFP-DD and OSFP are totally different form factors. For more information about QSFP-DD transceivers, you can refer to 400G QSFP-DD Transceiver Types Overview. You can use only one kind of form factor in the corresponding system. E.g., if you have an OSFP system, OSFP transceivers and cables must be used.
Q: What other breakout options are possible apart from using OSFP modules mentioned above?
A: OSFP 400G DACs & AOCs are possible for breakout 400G connections. See 400G Direct Attach Cables (DAC & AOC) Overview for more information about 400G DACs & AOCs.
Q1: What is the difference between QSFP28 ER4 and QSFP28 ER4 Lite Module?
A: The QSFP 100G ER4 has a series of BER requirements of better than 1E-12 without FEC optical modules. However, the receiving sensitivity of 100G QSFP28 ER4 is not satisfied with the existing APD technology. Therefore, many optical module manufacturers/suppliers defined a non-standard 100Gbase ER4 Lite module with a QSFP28 package where the largest transmission distance is up to 40km with FEC or 30km without FEC.?Walsun provides the QSFP28 100G ER4 Lite module compliant with the Ethernet 100Gbase ER4 Lite standard to meet the harshest external operating conditions including temperature, humidity, and EMI interference.
Q2: How does the QSFP 100G ER4 Module differ from the QSFP28 4WDM?
A: The QSFP 100G ER4 optical transceiver supports dual 100G Ethernet applications while the 100G QSFP28 4DWM only supports 100G Ethernet applications. The commons and differences are listed below.
| Form Type | QSFP28 ER4 | QSFP28 4WDM | ||
|---|---|---|---|---|
| Max Data Rate | 25.78125Gbps/27.95Gbps | 25.78125Gbps | ||
| Max Cable Distance | 40km | 10km | 20km | 40km |
| Center Wavelength | 1295.56nm, 1300.05nm, 1304.58nm, 1309.14nm | 1271nm, 1291nm, 1311nm, 1331nm | 1295.56nm, 1300.05nm, 1304.58nm, 1309.14nm | 1295.56nm, 1300.05nm, 1304.58nm, 1309.14nm |
| FEC Requirement | Without FEC (BER 1E-12) | With FEC (BER 5E-5) | ||
| Receiver | SOA+PIN ROSA | PIN ROSA | PIN ROSA | APD ROSA |
| Cooling Requirement | Cooled | Uncooled | Cooled | Cooled |
