Inline predistortion for both CSO and CTB correction

摘要

An inline predistortion circuit for producing composite second order (CSO) and composite triple beat (CTB) distortion correction of a laser transmitter is disclosed having an RF input signal, a diode for producing nonlinear current, and a DC voltage bias for controlling the nonlinear current. The predistortion circuit lacks DC blocking capacitors between the RF attenuator and the diode, which results in improved nonlinear current generation across a wide frequency range. A capacitor in parallel with the bias circuit further increases diode's capability for producing nonlinear current. A low resistance resistor in series with the RF signal path and in parallel with the diode provides the voltage necessary for the diode to conduct while minimizing RF signal attenuation. An inductor in series with the RF signal provides improved phase correction of the CSO and CTB predistortion circuit. A temperature compensation circuit is also integrated into the circuit to reduce the effect of temperature variations on the correction circuit.