Both 100GBASE-LR4 and 100GBASE-CWDM4 are Ethernet standards for 100 Gigabit per second (Gbps) data transmission, but they use different technologies and approaches. Let's break down the key differences between 100GBASE-LR4 and 100GBASE-CWDM4: 

1. Wavelengths and Multiplexing:

• CWDM4 stands for "Coarse Wavelength Division Multiplexing 4." This standard also uses four separate wavelengths, but in the CWDM grid. The wavelengths are typically in the range of 1271 nm to 1331 nm, with a channel spacing of 20 nm. Each wavelength carries a separate 25 Gbps data stream.

• LR4 stands for "Long Range 4." This standard uses four separate wavelengths in the 1294.53-1299.02 nm range for downstream transmission (from the network to the user) and four wavelengths in the 1309.14-1315.64 nm range for upstream transmission (from the user to the network). Each wavelength carries a separate 25 Gbps data stream.

• 100GBASE-LR4:

• 100GBASE-CWDM4:

2. Transmission Distance:

• CWDM4 is optimized for shorter-reach applications, typically up to 2 kilometers over single-mode fiber. It is well-suited for data center interconnects where shorter distances are common.

• LR4 is designed for longer-distance transmission, typically up to 10 kilometers over single-mode fiber (SMF). This makes it suitable for applications where longer-reach connectivity is required.

• 100GBASE-LR4:

• 100GBASE-CWDM4:

3. Multiplexing Technology:

• Utilizes Coarse Wavelength Division Multiplexing (CWDM) technology, where multiple signals with different wavelengths are combined onto a single fiber.

• Uses Wavelength Division Multiplexing (WDM) with separate wavelengths for each data stream.

• 100GBASE-LR4:

• 100GBASE-CWDM4:

4. Applications:

• Typically deployed in data center interconnects and shorter-reach applications where the benefits of CWDM can be leveraged.

• Commonly used for long-distance connections in telecommunications, metro, and regional networks.

• 100GBASE-LR4:

• 100GBASE-CWDM4:

In summary, while both 100GBASE-LR4 and 100GBASE-CWDM4 provide 100 Gbps data transmission, they differ in terms of the wavelengths used, the multiplexing technology applied, the achievable transmission distances, and the intended applications. The choice between them depends on the specific requirements and constraints of the network deployment.