>>>reasonableness<<<<

Hmmmmm......

Anyway, there is no real "conversion" of the data, only of the data format in the optical to electrical translation process. As Gonk said, the video issue does not apply here since in that case we would be dealing with analog signals of very high frequency which need a very clean and controlled signal path. Digital video data would behave like digital audio data and it would be extremely immune to degredation. Data formats are converted constantly - take the internet for instance, and yet you don't see massive errors for the same reason you don't see massive errors in digital audio - error correction schemes.