Isolator-free 2.5-Gb/s 80-km transmission by directly modulated /spl lambda//8 phase-shifted DFB-LDs under negative feedback effect of mirror loss

It was verified for the first time that phase-shift value in directly modulated DFB laser diodes (LDs) affects their chirping characteristics and external optical feedback resistance due to the feedback effect of mirror loss (FEML). Theoretical and experimental results clarified that the negative FEML achieved in /spl lambda//8 phase-shifted DFB-LDs was able to improve the transmission performances and make the LDs more robust to external optical feedback. Isolator-free 80-km transmissions with a very low power penalty of less than 1-dB at bit error rate (BER)=10/sup -10/ was demonstrated with 2.5-Gb/s directly modulated 1.55-μm /spl lambda//8 phase-shifted DFB-LDs.