Abstract

Recent years saw technology advances of large-capacity unrepeatered WDM transmission with a stretched ultra-long span. The main issues are the degradation of link OSNRs due to large span loss, and nonlinear impairments due to the launch of high power signals. At the line rate of 40 Gbit/s, unrepeatered WDM transmissions have been achieved mainly with effective-area-managed fi-bres.^1–4 Transmission fibres with effective areas as large as 175 µm² were used to reduce the impact of nonlinear penalties. On the other hand, a remotely pumped EDFA in the span, through the introduction of an extra pump fibre, had to be used sometimes.² System reaches of 250 km² and 306 km,⁴ and as high as 2.56 Tbit/s capacity¹ have been reported for the hybrid-fibre systems.

© 2002 Optical Society of America