40 Gbit/s, 1000 km dispersion-managed soliton transmission with dispersion tolerance of over 180 ps/nm

One of the most crucial considerations of a 40 Gbit/s transmission system is its small dispersion tolerance. For the non-return-to-zero modulation format signal the tolerable dispersion range is limited to about 75 ps/nm, and hence the bit error rate (BER) can easily be deteriorated by a small change in the dispersion of transmission fibers. On the other hand, it has been numerically shown that the dispersion management (DM) soliton has a wide tolerable range of the average dispersion. This feature is very attractive for high bit-rate systems, but the guideline to maximize the dispersion tolerance has not been derived. We study how the dispersion tolerance can be maximized by adjusting operating conditions in DM soliton transmission systems. It is theoretically shown that the dispersion tolerance is affected mainly by the pulse broadening and the soliton interaction, and that the largest dispersion tolerance is achieved by optimizing the pulse energy depending on the distance to be transmitted. According to our theory, we optimize the pulse energy for a given transmission distance of 1000 km, and demonstrate the 40 Gbit/s transmission with a dispersion tolerance of over 180 ps/nm using a recirculating loop setup