Degradation behavior of narrow-spectral-linewidth DFB lasers for super-wide-band FM conversion

The feasibility of using narrow-spectral-linewidth distributed-feedback lasers as subcarrier multiplexing video distribution sources in optical heterodyne FM converters is shown by investigating degradation modes of the lasers. There is no change in the dynamic properties, such as the FM response and the composite second-order and composite triple-beat figures, though spectral linewidth is increased by degradation. The main degradation appears as an increase in spectral linewidth due to 1/f noise caused by buried heterointerface degradation. The FM response, composite second-order, and composite triple-beat, however, hardly change in the degradation process.