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QSFP28 Optical Module Wiki
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With the development of science and technology, people's requirements on the rate of fiber optic communication are also increasing day by day, and now 100G optical modules are also applied in various scenarios.

There are various packaging forms of 100G optical modules, including CFP, CFP2, CFP4, CXP and QSFP28. Among these different packaging forms, QSFP28 optical module has become the main packaging form of 100G optical module due to its advantages of small size, high port density, and low cost, which is favored by enterprises, carriers and data centers.

- QSFP28 Optical Module Classification and Application

1. QSFP28 SR4 Optical Module

QSFP28 SR4 optical module is based on 100G Ethernet IEEE 802.3bm standard, which provides 4 independent transmit and receive channels, each supporting 25G, with a total bandwidth of 100G. the central wavelength is 850nm and adopts the MPO interface, which can transmit 70m on OM3 multimode fiber and 100m on OM4 multimodule fiber, which is suitable for short-distance transmission. short distance transmission. Because of its characteristics, QSFP28 SR4 optical module is mostly used in data centers, with multi-mode fiber in 100m distance for inter-switch cabling.

2. QSFP28 LR4 Optical Module

QSFP28 LR4 optical module is based on the 100G Ethernet IEEE 802.3ba standard. Unlike QSFP28 SR4, QSFP28 LR4 optical module adopts WDM technology, which multiplexes different wavelengths of four fiber channels into a single optical fiber for transmission, and the central wavelengths of four LAN WDM channels are 1295.56, 1300.05, 1304.58, 1309.58 and 1309.56 respectively. 1304.58 and 1309.14nm, the module adopts dual LC interfaces, with single-mode fiber transmission distance of up to 10km. suitable for medium and long distance transmission applications, mostly used in large-scale data centers and enterprise parks.

Figure 1  100G QSFP28

3. QSFP28 PSM4 Optical Module

QSFP28 PSM4 optical module is similar to QSFP28 SR4, providing 4 independent transmit and receive channels and adopting MPO interface, but the difference is that the center wavelength of QSFP28 PSM4 optical module is 1310nm, and with single-mode optical fiber, the maximum transmission distance is up to 2km. it should be noted that, the QSFP28 PSM4 optical module of MOTEK, in order to minimize the MPO connection, is suitable for medium and long distance transmission applications. In order to minimize the reflection caused by MPO connection, this product adopts MPO socket with 8-degree angled end face. This product should use a female MPO connector with an 8-degree endface.

4. QSFP28 CWDM4 Optical Module

QSFP28 CWDM4 Optical Module is similar to QSFP28 LR4. It adopts WDM technology to convert four 25Gb/s electrical data input channels into four CWDM optical signals and multiplexes them into a single channel to realize 100Gb/s optical transmission. Similarly, at the receiving end, the module multiplexes 100Gb/s input optical signals into 4 CWDM channels and converts them into 4 channels of output electrical data. 4 channels with central wavelengths of 1271, 1291, 1311, and 1331nm are used as LC interfaces, which can be transmitted over 2km with single-mode fiber.

5. QSFP28 ER4 Lite Optical Module

QSFP28 ER4 Lite optical module is based on 100G Ethernet IEEE 802.3bm standard, similar to the principle of QSFP28 LR4 optical module, which converts four 25Gb/s electrical signals into four LAN-WDM wavelengths of optical signals, which are coupled into a single optical fiber through the internal multiplexer (MUX) to complete the 100Gb/s optical signal transmission. However, the difference is that the QSFP28 ER4 Lite optical module adopts APD receiver, which is suitable for long-distance transmission.

 If the host used has the FEC function, the QSFP28 ER4 Lite can transmit up to 40km on the single-mode fiber of the optical module, and if the host used does not have the FEC function, the transmission distance is up to 30km.

Frequently Asked Questions

1、How to choose the best 100G QSFP28 optics?

For distances from 5 to 100 meters, you can choose QSFP28 SR4 optical transceiver modules. With OM3 fiber, data can be effectively transmitted up to 70 meters; with OM4 fiber, data can be effectively transmitted up to 100 meters.

If transmission needs are in the range of 100 meters to 2 kilometers, it is recommended to consider the suitability of QSFP28 100G PSM4 or QSFP28 CWDM4 modules. It is worth noting that while QSFP28 CWDM4 is significantly more expensive than QSFP28 PSM4, it has the advantage of bi-directional transmission utilizing only two single-mode fibers, which is significantly less costly than the MPO single-mode fiber optic cables required for QSFP28 PSM4. As a result, the total cost of implementing QSFP28 100G PSM4 may be significantly higher. The decision to choose QSFP28 PSM4 or QSFP28 CWDM4 should be based on the specific interconnect distance in the actual application.

For transmission distances from 10 to 40 kilometers, QSFP28 100G LR4 can be used, with a maximum transmission range of up to 10 kilometers.QSFP28 ER4 optical modules can achieve even longer distances, with a maximum transmission capacity of up to 40 kilometers.

2、Can 100G QSFP28 modules be connected downward?

Yes, 100G QSFP28 module can be connected with 25G optical module and 10G optical module. For example, 100G to 4*25G optical modules, 100G to 10*10G optical modules. The middle is connected with branch fiber optic cable.

3、Is 100G QSFP28 optical module compatible with various network equipment manufacturers?

Generally speaking, the design of 100G QSFP28 modules follows the industry standards set by organizations such as IEEE (Institute of Electrical and Electronics Engineers), which ensures a certain degree of compatibility between different network equipment manufacturers. This means that, in theory, 100G QSFP28 modules should be compatible with a wide range of network equipment from various manufacturers.

4. What are the power consumption considerations for 100G QSFP28 optical modules?

Power consumption considerations for 100G QSFP28 modules include module type, operating mode, link length, data rate, standby mode, cooling, power budget, data center efficiency, and future-proofing. Efficient power management is critical to optimize performance and reduce operating costs.

5、What types of optical connectors are used for 100G QSFP28 modules?

100G QSFP28 modules typically use LC duplex or MTP/MPO connectors for optical connections. LC duplex connectors are used for singlemode or multimode fiber connections, while MTP/MPO connectors are typically used for high-density multimode fiber connections, especially in data center environments. Connector selection depends on the specific application and cabling infrastructure.