Reduction of pulse-to-pulse interaction using alternative RZ formats in 40-Gb/s systems

We show that pulse-to-pulse interaction at 40 Gb/s can be reduced by alternating the optical phase of adjacent bits by using either a modified-duobinary return-to-zero (RZ) modulation format or RZ with alternating phase. Also, the generation of ghost pulses can be greatly suppressed using the modified-duobinary and duobinary RZ format.