2.5-Gb/s transmission characteristics of 1.3-μm DFB lasers with external optical feedback

All-optical networks will require low-cost laser sources. In order to reduce the packaging cost and to design a module without optical isolator, the 2.5-Gb/s 300-ps/nm transmission characteristics of 1.3-μm distributed-feedback lasers is analyzed in the presence of strong external optical feedback. The penalty degradation when the laser is operating under optical feedback is discussed and its dependence with the coherence collapse onset is analyzed. Although a drastic increase of the penalty with the coherence collapse state is reported, floor-free operation is demonstrated with a return loss as high as -8 dB.