Behind our digital world lie countless unseen optical fibers transmitting data. And the "core engine" connecting these fibers is the optical module. However, light experiences losses during transmission through optical fibers, much like the light from a flashlight weakens; the farther the light signal travels, the weaker it becomes. Therefore, engineers have designed optical modules with varying power outputs for different transmission distances.
So, how are the different transmission distances of optical modules represented? What do the letters mean?
SR indicates Short-Reach over Multimode Fiber，Generally, it's several tens of meters.Multimode fiber has a thicker core, allowing multiple light paths (modes). It's used for short-distance, high-speed connections, typically within a data center hall.
LR indicates Medium to Long-Reach over Single-Mode Fiber, Generally, it's 10 kilometers.Single-mode fiber has a very thin core, allowing only one light path. This results in lower loss and higher bandwidth, making it suitable for long-distance transmission.
ER indicates Extended Reach ~40 kilometers;ZR indicatesZealous / Longest Reach ~80 kilometers.XR indicates Extended Reach ~100 kilometers,Often a vendor-specific (e.g., Cisco) designation. They are not an official IEEE standard, but a common industry practice.
