Optical fiber interface for integrated circuit test system

A bi-directional interface with a first endpoint and a second endpoint for providing a first path and a second path between the first and second endpoints for transmitting signals between a circuit tester, at the first endpoint, and a connection point proximate to a circuit to be tested, at the second endpoint, the bi-directional interface comprising:

• a first link including a first optical fiber to provide a portion of the first path, the first link and the first optical fiber each having an input end and an output end;
• a second link including a second optical fiber to provide a portion of the second path, the second link and the second optical fiber each having an input end and an output end;
• a first directional gate for coupling both the input end of the first link and the output end of the second link to the first endpoint, and a second directional gate for coupling both the input end of the second link and the output end of the first link to the second endpoint, wherein the first directional gate comprises:
• a normally-closed switch disposed between the input end of the first link and the first endpoint;
• a normally-open switch disposed between the output end of the second link and the first endpoint;
• a sense switch coupled to the output end of the second link and connected, on sensing a signal from the second link, to cause the normally-open switch to close and the normally-closed switch to open;
• a delay line disposed between the output end of the second link and the normally-open switch, in parallel with the sense switch, and connecting the output end of the second link to the first endpoint when the normally-open switch is closed;
• a light source electrically coupled to the input end of the second link to receive electrical waveform signals from the circuit to be tested that appear at the second endpoint and operating to convert any received electrical waveform signals to light signals, the light source being optically coupled to the input end of the second optical fiber to transmit the light signals into the input end of the second optical fiber, the light source comprising a light emitter having a transfer function l(s);
• a photodetector optically coupled to the output end of the second optical fiber to receive light signals from the second optical fiber and electrically coupled to the output end of the second link to provide a reconstituted electrical waveform signal to the circuit tester;
• a receiver stage electrically coupled to receive an output of the photodetector;
• and
• an equalizer stage electrically coupled to receive an output of the receiver stage, the equalizer stage providing a transfer function 1/l(s).