All-optical signal processing for implementing network switching functions

In general, optical correlators can perform very fast signal processing. A header correlator is implemented as a hard-wired series of optical delay lines for which each header bit experiences a different optical delay. If a particular header bit has a corresponding "1" in the look-up table, then the delay will put that header bit inside an autocorrelation time window. If a header bit has a corresponding "0" in the look-up table, then the delay will put that header bit outside an autocorrelation time window. However, a key limitation is that the optical technology does not scale well, thereby making it practical for recognizing only a limited number of header bits. This may not be a significant drawback if only a few number of bits must be recognized in order to route packets to only a small number of ports.