Low crosstalk address encodings for optical message switching systems

An optical message switching system delivers messages from N sources to N destinations using beams of light. The redirection of the beams involves vector-matrix multiplication and a threshold operation. The authors consider the design of addresses which are both short (so that the number of threshold devices is reduced) and have low crosstalk (so that the sensitivity gap may grow). They show that addresses for O(log N) bits exist, for which the crosstalk is a constant fraction of the number of set bits in each address, hence allowing for a Theta (log N) sized sensitivity gap. More generally, they show the precise coefficient which depends on the desired gap. It is established that when using O(log N) bit addresses, the crosstalk cannot be further reduced. An exact construction of O(log² N) bit addresses is given, where the involved constant depends on the desired crosstalk. Finally they describe briefly the basic optical elements that can be used in order to construct a message switching system which use these address schemes.