Reduction of undesired harmonic components
Second-order predistortion circuit for use with laser diode
Optical transmitters linearized by means of parametric feedback
Apparatus and method for linearizing an external optical modulator
Predistortion method and apparatus for laser linearization
Method and apparatus for predistortion Patent #: 5361156
AbstractAn adaptive equalizer (also called a laser interface) for generating an electrical modulating signal for use by a laser to modulate an optical data signal. The laser has a non-linear modulation response pattern such that the optical data signal comprises a primary data signal and a plurality of harmonic distortion products. The adaptive equalizer operates by generating a correction electrical signal having a frequency equal to a frequency of one of the harmonic distortion products (this harmonic distortion product is nulled by operation of the adaptive equalizer). The adaptive equalizer detects the phase and amplitude of the harmonic distortion product. Then, the adaptive equalizer phase shifts the correction electrical signal in accordance with the detected phase such that the correction electrical signal and the harmonic distortion product are conjugately matched. The adaptive equalizer amplifies the phase shifted correction electrical signal in accordance with the detected amplitude such that the phase shifted correction electrical signal and the harmonic distortion product are equal in amplitude. Then, the amplified and phase shifted correction electrical signal is combined with an electrical data signal to form the electrical modulating signal.