Abstract: An electrical compensation circuit and an optical compensation circuit are provided for compensating for expansion-type and compression-type gain distortion due to the interaction of a laser and an optical amplifier. In the electrical compensation circuit there is provided a linear signal path and a nonlinear signal path. A delay circuit in the linear signal path compensates for a signal delay in the nonlinear signal path. In the nonlinear signal path there is provided an FET and a transformer. A modulation signal applied to the linear signal path and the nonlinear signal path is processed in the nonlinear signal path and combined with the signal in the linear signal path so as to provide a predistorted modulation signal which is substantially equal in amplitude and opposite in phase to the gain distortion in the optical signal at the output of the optical amplifier.

Abstract: An electrical compensation circuit and an optical compensation circuit are provided for compensating for expansion-type and compression-type gain distortion due to the interaction of a laser and an optical amplifier. In the electrical compensation circuit there is provided a linear signal path and a nonlinear signal path. A delay circuit in the linear signal path compensates for a signal delay in the nonlinear signal path. In the nonlinear signal path there is provided an FET and a transformer. A modulation signal applied to the linear signal path and the nonlinear signal path is processed in the nonlinear signal path and combined with the signal in the linear signal path so as to provide a predistorted modulation signal which is substantially equal in amplitude and opposite in phase to the gain distortion in the optical signal at the output of the optical amplifier.

Abstract: A delay distortion compensating circuit for a laser driven optical transmission system comprises a varactor network for producing a time shift of the instantaneous amplitude of the modulation signal applied to the laser that is inverse to the time shift caused by chromatic dispersion of a fiber optic cable used for propagating the output of the laser and laser chirp so that the sum of the two time shifts is substantially equal to a constant. In one embodiment the cathode of the varactor diode is coupled to a center tap of an inductor called a first order delay equalizer, the terminals of which are connected to a source of a modulating signal and the laser. A d-c bias is applied to the varactor by means of a choke. In another embodiment called a low pass structure, a modulating signal is coupled to the laser through an inductor and a parallel combination of a discrete capacitor and a varactor diode is coupled between ground and a node located between the inductor and the laser.