High Optical-Feedback Tolerance of Distributed Reflector Lasers With Wirelike Active Regions for Isolator-Free Operation

The optical-feedback tolerance of distributed reflector laser with a wirelike distributed feedback section and a distributed Bragg reflector section was investigated. A very high critical feedback level of ${-}$12.5 dB and low relative intensity noise were confirmed. Isolator-free 2.5-Gb/s to 10-km transmissions were demonstrated under ${-}$13.5-dB optical back-reflection with a power penalty of 2 dB.