Raynet Corporation

Peter W Cornish

Gregory S Maurer

Richard M Murphy

Barry Duncan

A predistortion circuit reduces composite second order intermodulation distortion products inherently generated by a laser diode. A radio frequency signal is split into a primary and secondary signal, and the secondary signal is amplified by an amplifier biased at a starvation current level so as to produce intermodulation distortion products having an amplitude relatively large compared to an amplitude of a fundamental generated by the amplifier. The amplitude and phase of composite second order intermodulation distortion products generated by the amplifier are adjusted so as to substantially match those inherently generated by the laser diode by the primary electrical signal, with the products being about 180.degree. out of phase relative to those generated by the laser in response to the primary signal. The adjusted distortion products are combined with the primary electrical signal, and the combined signal is fed to the laser diode resulting in an output of the laser diode having minimum composite second order intermodulation distortion products.

Predistortion method and apparatus for laser linearization

A linear optical broadband signal generator includes primary and secondary optical modulators whose outputs are combined so as to minimize intermodulation distortion of a modulated optical signal. A constant amplitude optical signal is split differentially so as to create primary and secondary power levels, the primary and secondary power levels being inputted into the primary and secondary modulators. An electrical input to one of the modulators is differentially attenuated so as to reduce third order modulation products when modulated outputs of the modulators are combined. In addition, the total modulated optical output power is maximized by adjustment to one of the outputs of one of the modulators so that its phase is more in line with a phase of the output of the other modulator so as to maximize first order products of the combined output.

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Pleasanton, CA, United States of America

Peter W Cornish