$pi/2$ Alternate-Phase On–Off Keyed 42.7 Gb/s Long-Haul Transmission Over 1980 km of Standard Single-Mode Fiber

The authors present 42.7-Gb/s return-to-zero on-off keying pulse-overlapped 1980-km transmission experiments on standard single-mode fiber, which compare the performances of the 33% duty-cycle /spl pi//2 alternate-phase format to the 33% duty-cycle return-to-zero and the 67% duty-cycle carrier-suppressed return-to-zero on-off keying formats. The results show that an effective reduction in nonlinear transmission penalty from intrachannel four-wave mixing can be achieved in systems where strong pulse overlap occurs. Experiments show an increased optimum launch power of 2 dB can be realized with the /spl pi//2 alternate-phase format resulting in a >3 dB improvement in Q as compared to the return-to-zero and carrier-suppressed return-to-zero formats due to a reduction in intrachannel four-wave mixing.