Power Fluctuations in the Side Modes of Injection Lasers

Small side modes which contain on the average only a few percent of the total output of injection lasers can cause high bit-error rates through power fluctuations. By measuring the RF spectrum and the bandwidth dependence of the statistical power distributions, we have clarified the nature of these fluctuations. We find that although a laser is driven above threshold, an individual small side mode behaves like a chaotic light source, i.e., a laser biased below threshold.