Distortion characteristics in directly modulated laser diodes by microwave signals

A simple method for determining the harmonic and intermodulation distortion characteristics of a laser diode under direct modulation by microwave analog signals is presented and experimentally verified. The method makes use of small-signal perturbation analysis of the rate equations to obtain analytical expressions for the distortion. The parameters that are required for the calculation of distortion characteristics are the damping factor and resonant frequency of the intrinsic laser diode, and they are derivable from the small-signal modulation response of the actual laser using a de-embedding procedure. The method has been experimentally verified using DFB (distributed feedback) laser diodes operated at 1.3 and 1.5 mu m wavelengths with modulation frequencies up to 6 GHz.<
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