RELIABILITY AND DEGRADATION BEHAVIOR OF HIGHLY COHERENT 1.55-MU-M LONG-CAVITY MULTIPLE QUANTUM-WELL (MQW) DFB LASERS

Degradation behavior and reliability of 1.55-mu-m highly coherent MQW DFB lasers with a long-cavity are examined and clarified. The increase in spectral linewidth, due to the increase in 1/f noise and internal optical loss and the instability of side mode, and the changes in FM response, especially increase in FM efficiency, occur during degradation, e.g., increase in threshold current. In addition to these basic degradations, the degradation behavior of multisection DFB lasers are also clarified from the viewpoint of device characteristics, such as wavelength tunability. By clarifying these changes in device characteristics, the possibility of long life for long-cavity MQW DFB lasers in optical coherent transmission systems is shown.