Abstract
Passive optical network topology has been widely adopted in access networks due to its low-cost and yet flexible network structure. To further promote the passive optical networks, the cost reduction of optical modules is critical. Relatively expensive combination of a conventional index-coupled distributed feedback laser diode (IC-DFB-LD) and an optical isolator is commonly used for passive optical networks with transmission distance more than 30km. Although gain-coupled DFB-LDs (GC-DFB-LD) have been widely investigated in the hope of eliminating the isolator in optical modules, their limited output power keeps them from practical use in passive optical networks. In this paper, we describe the development of 1.31µm and 1.49µm GC-DFB-LDs with high output power and optical feed back tolerance for isolator-free optical modules in access networks. The relative intensity noise (RIN) degradation was well suppressed below -120dB/Hz at -8dB optical feedback in the temperatures range from 0°C to 85°C from both 1.31µm and 1.49µm GC-DFB-LDs. Optical feedback tolerance of 1.31µm and 1.49µm GC-DFB-LDs were improved by more than 6dB and 4dB as compared with conventional IC-DFB-LDs. Dispersion power penalty after over 30km transmission at 1.25Gbps were achieved less than 0.3dB and 0.7dB under -15dB optical feedback conditions. The proposed 1.31µm GC-DFB-LD prototypes experimentally demonstrated 14mW output power with over 5, 000-hour operation at 85°C. Our devices are found to fully complying IEEE 802.3ah standard and seem to be promising for the low-cost optical modules in long-reach access network applications. The details of the device structure as well as transmission experiments are also reported.
