100G CWDM4 QSFP28 Transceiver Module
100G CWDM4 QSFP28 is a standard published by the CWDM4 MSA organization in 2014.
It is a 100G transmission mode based on single-mode coarse wavelength division multiplexing (CWDM) technology. The 100G CWDM4 QSFP28 optical module conforming to this standard adopts a duplex LC interface and uses 4 central wavelengths of 1271nm, 1291nm, 1311nm and 1331nm for optical Signal transmission (see the table below), each band transmits 25G.
Through coarse wavelength division multiplexing (CWDM) technology, the 100G CWDM4 QSFP28 optical module can multiplex the above four central wavelengths onto a single-mode optical fiber for transmission.
It should be noted that, in order to ensure the stability of the optical fiber transmission system, 100G CWDM4 QSFP28 optical modules must be used for optical fiber links with forward error correction (FEC).
| Wavelengths channel | Center wavelength | The range of wavelength | |
| Lane1 | 1271 | 1264.5 to 1277.5 nm | Tx0, Rx0 |
| Lane2 | 1291 | 1284.5 to 1297.5 nm | Tx2, Rx2 |
| Lane3 | 1311 | 1304.5 to 1317.5 nm | Tx3, Rx3 |
| Lane4 | 1331 | 1324.5 to 1337.5 nm | Tx4, Rx4 |
The 100G CWDM4 QSFP28 optical module adopts QSFP28 package, which is a hot-swappable optical module, and the transmission distance can reach 2 km when used with single-mode fiber.
Compared with the 100G LR4 QSFP28 optical module with a transmission distance of 10 km, the price of the 100G CWDM4 QSFP28 optical module is much lower, and it can meet a variety of long-distance transmission requirements in data centers.
100G CLR4 QSFP28 Transceiver Module
100G CLR4 QSFP28 is a 100G optical module standard formulated by the 100G CLR4 Alliance. It is similar to the 100G CWDM4 QSFP28 optical module. This optical module also uses single-mode coarse wavelength division multiplexing (CWDM) technology, using duplex LC interface, and single-mode optical fiber. The transmission distance used together is also 2 km.
The difference is that the 100G CLR4 QSFP28 optical module can be used not only for fiber links with forward error correction (FEC), but also for fiber links without forward error correction (FEC).
For fiber optic links with forward error correction (FEC) functions, 100G CWDM4 QSFP28 optical modules and 100G CLR4 QSFP28 optical modules can be used together.
In fiber links without forward error correction (FEC), the 100G CLR4 QSFP28 optical module can also maintain low latency and low power consumption. This feature of 100G CLR4 QSFP28 optical module makes it more popular in high-performance computing, high-frequency trading and other fields.
100G CWDM4 QSFP28 Transceiver Module VS 100G CLR4 QSFP28 Transceiver Module
The 100G CWDM4 QSFP28 optical module and the 100G CLR4 QSFP28 optical module have basically the same working principle, operating wavelength, and operating temperature. The following table shows the basic parameters and application scope of these two optical modules as shown in the table below:
| Transceiver Module | Operating wavelength(nm) | The transmission rate of different channel(Gbps) | Operating temperature(°C) | Power consumption (W) | Transmission distance(km) | Forward error correction (FEC) | Application |
| 100G CWDM4 QSFP28 | 1270/1290/1310/1330 | 25.78125 | 0-70 | 2.6 | <=2 | Need | General application |
| 100G CLR4 QSFP28 | 1270/1290/1310/1330 | 25.78125 | 0-70°C | 2.6 | <=2 | Optional | High-performance computing, high-frequency trading and other fields |
Conclusion
100G CWDM4 QSFP28 optical module and 100G CLR4 QSFP28 optical module are cost-saving solutions in data center 2 km transmission applications.
Among them, 100G CWDM4 QSFP28 optical modules are more common in data centers.