Optical bus using controllable optical devices

An optical bus interface device adapted to be interposed in an optical transmission medium, comprising:

• an active coupler having first, second, third, and fourth ports and a control element, said control element being responsive to input signals and operable to place said coupler in either of at least first and second states;
• said first state preventing a significant fraction of light from said first port from reaching said second port and preventing a significant fraction of light from said second port from reaching said first port;
• said second state coupling a significant fraction of light from said first port to said second port, a small fraction of light from said first port to said fourth port, a significant fraction of light from second port to said first port, and a small fraction of light from said second port to said third port;
• a transmitter unit for applying control signals to said control element, for selectively placing said coupler in a desired state;
• and
• a receiver unit, responsive to light at said third and fourth ports of said coupler, for providing signals representative of the light at said third and fourth ports.

An optical bus for a computer system having a plurality of functional units, the bus having two ends designated the left end and the right end, comprising:

• a plurality of active couplers, each having first, second, third, and fourth ports and a control element, said control element being responsive to input signals and operable to place said coupler in either of at least first and second states;
• said first state preventing a significant fraction of light from said first port from reaching said second port and preventing a significant fraction of light from said second port from reaching said first port;
• said second state coupling a significant fraction of light from said first port to said second port, a small fraction of light from said first port to said fourth port, a significant fraction of light from second port to said first port, and a small fraction of light from said second port to said third port;
• and
• means for optically connecting said couplers in a serial fashion to define a bus line with one of said couplers being the leftmost coupler and another of said couplers being the rightmost coupler, wherein each coupler has its first port in optical communication with the second port of the coupler to the left, if any, and its second port in optical communication with the first port of the coupler to the right, if any;
• means for injecting light into the first port of the leftmost coupler and into the second port of the rightmost coupler;
• a plurality of transmitter units, each for applying control signals to a different respective one of said control elements, for selectively placing the respective coupler in a desired state;
• and
• a plurality of receiver units, each responsive to light at said third and fourth ports of a different respective one of said couplers, for providing signals representative of the light at said third and fourth ports when the respective coupler is in said second state.

An optical device adapted to be interposed in an optical transmission medium, comprising:

• an active coupler having first and second ports, an additional port, and a control element, said control element being responsive to input signals and operable to place said coupler in either of at least first and second states;
• said first state preventing a significant fraction of light from said first port from reaching said second port;
• said second state coupling a significant fraction of light from said first port to said second port and coupling a small fraction of light from said first port to said additional port;
• and
• a photodetector in optical communication with said additional port of said coupler.

An optical bus for a computer system having a plurality of functional units, the bus having two ends designated the left end and the right end, comprising:

• a plurality of active couplers, each having first and second ports, an additional port, and a control element, said control element being responsive to input signals and operable to place said coupler in either of at least first and second states;
• said first state preventing a significant fraction of light from said first port from reaching said second port;
• said second state coupling a significant fraction of light from said first port to said second port and coupling a small fraction of light from said first port to said additional port;
• and
• a photodetector in optical communication with said additional port of said coupler;
• means for optically connecting said couplers in a serial fashion to define a bus line with one of said couplers being the leftmost coupler and another of said couplers being the rightmost coupler, wherein each coupler has its first port in optical communication with the second port of the coupler to the left, if any, and its second port in optical communication with the first port of the coupler to the right, if any;
• means for injecting light into the first port of the leftmost coupler;
• a plurality of transmitter units, each for applying control signals to a different respective one of said control elements, for selectively placing the respective coupler in a desired state;
• and
• a plurality of receiver units, each responsive to light at said additional port of a different respective one of said couplers, for providing signals representative of the light at said additional port when the respective coupler is in said second state.

A method of establishing bus communication among a plurality of functional units, the bus having two ends designated the left end and the right end, comprising:

• providing a plurality of active couplers, each having first and second ports, an additional port, and a control element, said control element being responsive to input signals and operable to place said coupler in either of at least first and second states;
• said first state preventing a significant fraction of light from said first port from reaching said second port;
• said second state coupling a significant fraction of light from said first port to said second port and coupling a small fraction of light from said first port to said additional port;
• optically connecting said couplers in a serial fashion to define a bus line with one of said couplers being the leftmost coupler and another of said couplers being the rightmost coupler, wherein each coupler has its first port in optical communication with the second port of the coupler to the left, if any, and its second port in optical communication with the first port of the coupler to the right, if any;
• injecting light into the first port of the leftmost coupler;
• selectively applying control signals to said control elements, for selectively placing the respective couplers in a desired state;
• and
• detecting light at said additional ports of said couplers, thereby providing signals representative of the light at said additional ports when the respective couplers are in said second state.