System and method for minimizing nonlinear distortion in optical communication systems employing laser intensity modulation

摘要

An amplitude limiting circuit is utilized to select the most favorable linear region of the light vs. current characteristic curve (for directly modulated lasers) or the lasers modulator transfer function (for externally modulated lasers) by preventing excursions of the broadband, multiplexed input signal beyond selected upper and lower current or voltage limits. The clipped broadband signal is represented as a stationary Gaussian process to provide a reliable estimate of the carrier- to-nonlinear distortion per channel that would be experienced with a given laser or optical modulator which may be either directly and externally modulated. The clipping levels can be set to avoid the unpredictable levels of nonlinear distortion of the modulator and thereby to achieve an acceptably low level of non-linear distortion of the modulator.