Fault tolerant optical cross-channel data link

Claim 1

A cross-channel data link which is operable to provide communication between plural computing elements of a fault tolerant computing system, said cross-channel data link comprising: a multiplicity of nodes interconnected in a ring configuration, each node being coupled to a clockwise adjacent node via a single optical fiber and to a counterclockwise adjacent node via a different single optical fiber and each node being coupled to one of the computing elements of the fault tolerant computing system, said nodes each including: a first and second optical transmitter, a first and second optical receiver, a first wavelength division multiplexing means coupled to said first optical transmitter and said first optical receiver for multiplexing an optical signal transmitted by said node and traveling in a clockwise direction with an optical signal received by said node traveling in a counterclockwise direction through the single optical fiber joining the clockwise adjacent nodes, a second wavelength division multiplexing means coupled to said second optical transmitter, and said second optical receiver for multiplexing an optical signal transmitted by said node and traveling in a counterclockwise direction with an optical signal received by said node traveling in a clockwise direction through the single optical fiber joining the counterclockwise adjacent nodes, controller means coupled to one of said plural computing elements for exchanging data indicative of the instantaneous state of said plural computing elements, a two-stage modulator coupled to said controller and to said first and second transmitters, and a two-stage demodulator coupled to said controller and to said first and second optical receivers.