Statistical properties of the spectrum of light pulses in fast pseudorandom word modulation of a single-mode semiconductor laser

The spectrum of single-mode laser pulses generated by fast pseudorandom word modulation is studied numerically for return-to-zero and nonreturn-to-zero control signals. We analyze both statistics and the worst cases for the frequency chirp during each optical pulse, and we study the connection between these frequency chirps and the turn-on times. We show that patterns in the modulation signal sequences contribute to chirp noise. The worst case values of the turn-on time and the chirp range are very similar in the two modulation schemes, hence, the optimum choice depends mainly on the characteristics of the decision circuit and on the driver and detector bandwidths