Timing jitter of ultrashort solitons in high-speed communication systems .2. Control of jitter by periodic optical phase conjugation

We consider the use of periodic optical phase conjugation for reducing the timing jitter in high-speed fiber-optic communication systems employing ultrashort solitons (width < 10 ps) in dispersion-decreasing fibers. Using adiabatic perturbation theory, we derive analytically an expression for the trajectory of a periodically conjugated ultrashort soliton in a communication link after including the effect of amplifier noise and use it to derive the timing jitter in the soliton arrival time at the end of a transmission line. The analysis takes into account not only the group-velocity dispersion but also the Raman effect and the third-order dispersion. We show that the timing jitter can be minimized by using an optimized amplifier spacing (similar to 65-80 km) for a specific value of average fiber dispersion. The use of shorter amplifier spacings increases timing jitter because of third-order dispersion while for larger amplifier spacings the increased jitter originates fr om the Raman effect. For high-bit rate systems considered in this paper the Gordon-Haus contribution to the timing jitter is negligible. Under optimized conditions, nearly error-free transmission can be realized at a bit rate of similar to 100 Gb/s over a distance of 1200 km even in the absence of optical filters. We discuss the role of optical filters for improving system performance and the impact of fiber-dispersion fluctuations on the periodic filtering of ultrashort solitons. (C) 1997 Optical Society of Amerca.