Predistortion circuit including distortion generator diodes with adjustable diode bias

An optical system comprising:

• a RF signal input configured to provide a RF input signal;
• a predistortion circuit configured to receive the RF input signal and to generate a predistorted RF input signal, the predistortion circuit comprising:
• a primary signal path configured to receive at least a portion of the RF input signal;
• and
• a secondary signal path coupled to the primary signal path and configured to receive at least a portion of the RF input signal, the secondary signal path comprising a second order distortion generator configured to produce predistortion from the RF input signal, the second order distortion generator comprising at least first and second diodes;
• a laser configured to receive the predistorted RF input signal and to generate a modulated optical output, wherein the predistorted RF input signal compensates for the distortion generated by the laser;
• and
• an adjustable bias control coupled to the first and second diodes, the adjustable bias control being configured to adjust a bias current provided to the diodes to adjust a magnitude of the predistortion such that the adjustable bias control provides the only control for adjusting the magnitude of the predistortion, wherein the predistortion is capable of compensating for distortion generated by the laser at a highest frequency component of interest.