1.28 Tbit/s—70‐km OTDM femtosecond‐pulse transmission using third‐ and fourth‐order simultaneous dispersion compensation with a phase modulator

By means of the higher‐order dispersion compensation technique using a phase modulator, a 70‐km transmission experiment with 1.28 Tbit/s OTDM (Optical Time Domain Multiplexing) signals has been successfully conducted for the first time. The details are reported in this paper. The 1.28 Tbit/s signal is obtained by 64‐fold multiplexing of 10 Gbit/s signals with additional polarization multiplexing. For the signal pulse with a pulse width of 380 fs prior to transmission, a linear chirp is imparted and then a cosine phase modulation with an appropriate amplitude and the timing is set in such a way that the imparted chirp is opposite to the chirps caused by the third‐ and fourth‐order dispersion in the transmission path. In this way, the waveform distortion of the signal due to the third‐ and fourth‐order dispersion can be suppressed simultaneously. The pulse widening of the signal after transmission over 70 km is only 20 fs. Hence, an error rate of less than 1 × 10−9can be realized over the entire channel (10 Gbit/s–128 channels after multiplexing separation).