Adaptive modeling of laser diode nonlinearity with memory

Direct modulation of laser diode in radio-over-fiber applications offers a cost effective solution compared to modulation by external devices. Laser diode nonlinearity is the biggest challenge, however, with direct modulation. Previous work has proposed adaptive pre/post compensation of laser diode nonlinearity based on a third order Volterra filter without memory. In this paper, the memory effect of the laser diode is studied by solving the rate equations. It is found that the memory effects of the laser diode are significant with modulating frequencies 10 MHz and above. A seventh order Volterra filter with nine memory terms models the laser diode nonlinearity when the input is 20 MHz with an accuracy of 0.01%.