Abstract

Injection lasers usually have an output consisting of several longitudinal modes.⁽¹⁾ Depending on the relative strength of these modes, injection lasers can be classified as multimode or single-mode lasers. So-called single-mode lasers have an output consisting of a dominant mode and several small but measurable side modes. The power in each side mode can be very small, 1% or even 0.1% of the total output, nevertheless, these side modes are always present. This is true even for DFB lasers. The side modes are small only on the average sense. They fluctuate and can become the major mode momentarily. When the laser output is coupled into a dispersive fiber, these fluctuations become mode partition noise⁽²⁾ and can cause large error rate.

© 1984 Optical Society of America