2. Parameters affecting transmission quality

2.1 FEC Q limit

The transmission quality required by the user is high, as the submarine links constitute the main transmission arteries that then feed the terrestrial links to the subscriber:

The quality of the digital signal delivered by a submarine link must be such that the error rate is less than 10- ¹³ , i.e. Q greater than 17.3 dB.

However, the introduction of Forward Error Correction (FEC) codes in submarine link terminals significantly lowers the level of transmission quality required at the output of the submarine link.

The minimum Q factor required before correction to obtain Q = 17.3 dB after correction is called Q _FEC ...