We demonstrated variable dispersion compensation using the Virtually Imaged Phased Array (VIPA) for a 40-Gbit/s dense-WDM transmission system. The large tunable range from -800 to +800 ps/nm in the entire C-band wavelength range and the high tunable resolution of 1 ps/nm was achieved by using a 3-dimensional mirror equipped with a stepping motor that we developed. We adopted the dispersion monitor of 40-GHz intensity extracted from the received 40-Gbit/s baseband signals, and verified that this dispersion monitoring method is applicable to nonlinear transmission by detecting the monitor peak. Using the VIPA variable dispersion compensator and the dispersion monitor, we demonstrated 1.28-Tbit/s (40-Gbit/s 32 ch) automatic dispersion compensation. As a result, we confirmed that only two VIPAs and one fixed dispersion compensating fiber (DCF) are needed to make our method applicable to the entire C-band for dense WDM 40-Gbit/s systems having a large transmission range of 80 km.

This paper proposes that a combination of pre-chirping and dispersion compensation is effective in suppressing the waveform distortion due to the self-phase modulation and the group-velocity dispersion in 10 Gb/s repeaterless transmission using 1.3-µm zero-dispersion single-mode fibers (SMF) operating at a wavelength of 1.55µm. The following results were obtained through simulation. 1) Setting the α-parameter of a LiNbO3 optical modulator negative (α1.0) gives a large tolerance of the launched power Pin. 2) For 90-km SMF transmission, the maximum Pin is obtained when the dispersion compensation ratio β is from 50% to 70%. 3) For the allowable β as a function of the transmission distance when a dispersion compensator is located in the receiver (post-compensation scheme), the lower limit of β is determined by the constant residual dispersion value, which agrees well with the dispersion tolerance without dispersion compensation. Our 90-km SMF transmission experiments using a LiNbO3 optical modulator and a dispersion compensating fiber (DCF) confirmed the simulation results regarding the optimum value of β and the large tolerance of the fiber launched power. Based on the above investigations, we achieved a 10-Gb/s repeaterless 140-km SMF transmission with α1.0 and post-compensation.