Mode partition noise of nearly single-mode semiconductor lasersmodulated at GHz rates

A new method to calculate very low errors due to mode partition noise in nearly single-mode semiconductor lasers has been developed. The laser is intensity modulated at GHz rates. The method allows us to obtain the error for a periodic sequence of input bits as a function of the threshold gain difference for different values of the bias current, above and below threshold, injected current in the ON state and modulation frequency. It is shown that bounds for the error under pseudorandom modulation conditions can be obtained from the periodic and gain switching sequences. The required threshold gain difference for an error of 10^-9 is calculated, and it is shown to increase with the current in the ON state. We also observe pattern effects at the output of the laser, for bias current above threshold, due do the pseudorandom sequence of input bits. For a special value of the bias current slightly below threshold, these patterns effects are suppressed and the error is independent of the modulation frequency and of the modulation regime