Enhancement of Optical-Feedback Tolerance of SOA-Integrated EML (AXEL) by Introducing DBR-Type Laser

A DBR-laser-based SOA-assisted extended-reach EML (AXEL) was investigated in order to improve the optical feedback tolerance. The performance was tested in relative intensity noise measurement and fiber transmission experiment. A superior optical feedback tolerance was obtained in comparison with a conventional AXEL. The excess RIN induced by optical feedback is suppressed at 3-dB higher feedback power for the DBR-AXEL. 40 km fiber transmission of 10-Gbit/s signal with a feedback factor of −15 dB was achieved. The power budget was 41.3 dB. The feedback-induced power penalty was 0.52 dB.