Modelling and simulation of high-speed direct detectionoptical fibre communication systems

A simulation strategy suitable for performance assessment of long-haul high-bit-rate direct-detection systems is presented. Particular consideration is given to the interaction with fiber dispersion of laser modulation phenomena such as frequency chirp and patterning which exhibit complex nonlinear data dependence. The nonlinear modulation response of the laser transmitter is taken into account by using pseudo-random data sequences to estimate the dispersion-induced performance degradation. The dependence of the modulation and dispersion-induced penalties on the extinction ratio of the laser emission is shown for the specific case of 4 Gb/s NRZ modulation and a total dispersion L×D=1 ns/nm. With this approach, the implications for system performance of the laser operating point, modulation format used, receiver filter bandwidth, and timing acquisition imperfections are investigated, and some performance limitations are indicated