The Nyquist signaling rate only applies to binary/two-level signals. Most optical communications systems use many levels to improve the data rate. StackExchan

The Nyquist signaling rate only applies to binary/two-level signals. Most optical communications systems use many levels to improve the data rate. StackExchange discussion: http://electronics.stackexchange.com/questions/21854/why-is-the-nyquist-data-rate-lower-than-the-shannon-data-rate http://electronics.stackexchange.com/questions/21854/why-is-...