Millimeter-wave generation and digital modulation in an InGaAs-InP heterojunction phototransistor: Model and experimental characterization of dynamics and noise

This paper describes the use of an InGaAs-Inp photoheterojunction bipolar t ransistor (photo-HBT) for millimeter-wave generation and digital modulation . Optical mixing of two coherent signals generates the carrier, and a digit al drive signal to the base is used for the modulation. We describe an adva nced large signal model of the photo-HBT that takes into account distribute d effects at high frequencies and all noise sources, including optical ampl ifier noise and noise correlations due to the high operation frequency and the nonlinear mixing processes. The model enables one to predict carrier-to -noise ratio dependence on frequency, optical power, and the transistor ope rating point. Frequency- and time-domain responses of the modulated millime ter- wave carrier and bit error rates are also calculated. Experiments at 1 0 and 45 GHz with modulation rates ranging between 50 Mb/s and 2.5 Gb/s wer e performed, and a superb fit to the calculated responses is found.