What is Forward Error Correction (FEC) primarily used for on high-speed optical links?

• A. Error detection only at the receiving end.
• B. Forward Error Correction used by high-speed optics to correct bit errors in flight.
• C. Monitoring cable temperature to prevent failures.
• D. Traffic shaping at the switch.

Answer: (B)

Forward Error Correction is a technique used to keep data accurate on a high-speed optical link by correcting errors as the data is being received. As signals travel through fiber, noise and impairments cause occasional bit flips. FEC adds extra parity information to the transmitted data, allowing the receiver to detect and repair those bit errors without needing a retransmission. This keeps throughput high and reduces latency, which is crucial at fast data rates and over longer distances. It’s different from simple error detection methods (which only flag errors) and from unrelated practices like monitoring temperature or shaping traffic, which don’t fix bit errors on the fly.