Operation of diode-clamped FET-SEED optical receivers with low-contrast single-ended signals

We report an experimental study of the contrast ratio needed for single-ended operation of diode-clamped optical receivers. These receivers, realized in field-effect-transistor-self-electrooptic-effect device (FET-SEED) technology, are high impedance FET-based receivers designed to operate with two optical beams in prototype smart-pixel systems. Single-ended data can be supplied to these devices by operating them, with a clock beam on one detector and a signal beam on the other detector in a return-to-zero (RZ) format. We find that with the use of this clock beam, the receiver can operate successfully with optical data having contrast ratios less than 2 at rates as high as 300 Mb/s, or at sensitivities as high as 20 fJ at 300 Mb/s. Simple models of the thresholding behavior of the circuit explain this result.