The main difference between 100G LR4 (Long Range 4) and 100G SR4 (Short Range 4) lies in the type of fiber they are designed to work with, the transmission distance they support, and the optical wavelengths used. These are two different types of 100 Gigabit Ethernet transceivers used in data center and high-speed networking applications. Here's a breakdown of their key characteristics: 

1. Fiber Type:

• 100G LR4: LR4 transceivers are designed for use with single-mode fiber (SMF). Single-mode fiber is optimized for longer-distance transmissions and typically has a narrower core, allowing signals to travel over greater distances without significant attenuation.

• 100G SR4: SR4 transceivers, on the other hand, are designed for use with multimode fiber (MMF). Multimode fiber is commonly used for shorter-distance connections within data centers.

2. Transmission Distance:

• 100G LR4: LR4 modules are designed for long-range transmissions, typically supporting distances up to 10 kilometers (km) over single-mode fiber.

• 100G SR4: SR4 modules are optimized for short-range connections, typically supporting distances up to 100 meters (m) over multimode fiber.

3. Wavelengths:

• 100G LR4: LR4 modules use four separate wavelengths, commonly around 1295.56nm, 1300.05nm, 1304.58nm, and 1309.14nm. These wavelengths are multiplexed onto a single fiber for bidirectional communication.

• 100G SR4: SR4 modules use four separate wavelengths centered around 850nm. These wavelengths are typically used with parallel optics, where each wavelength corresponds to a separate optical lane.

4. Connector Type:

• Both LR4 and SR4 modules commonly use MPO/MTP connectors. However, it's important to note that the specific connector type might vary based on the manufacturer and product specifications.

In summary, the choice between 100G LR4 and 100G SR4 depends on the specific requirements of the network, including the distance between devices and the type of fiber infrastructure in use. LR4 is suitable for longer-range connections over single-mode fiber, while SR4 is designed for shorter-range connections over multimode fiber.