Timing jitter in a long-haul 40 Gb/s dispersion-managed soliton system

We successfully compared experiment and simulation of a 40 Gb/s dispersion-managed soliton (DMS) system in a recirculating loop. We used periodic dispersion compensation and a 3.8 nm optical inline filter. Reducing the data rate to 10 Gb/s, while keeping other parameters constant, we were able to isolate the impact of inter-symbol interference (ISI). Timing jitter and ISI are strongly coupled in our loop and limit the propagation distance. Our results demonstrate the increased care that is needed to correctly design and model systems with a single-channel data rate of 40 Gb/s as compared to systems with 10 Gb/s. In particular, we found that path average dispersion, EDFA placement, filter center wavelength, and optical power must be precisely adjusted to optimize transmission. Once we had understood and controlled all the key parameters, we were able to achieve excellent agreement between theory and experiment and error-free propagation over distances of about 6,300 km. Beyond this distance, our simulation shows that the probability distribution of the receiver voltage starts to deviate from a Gaussian shape and hence the Q-factor as a figure of merit becomes unreliable.