The future of optically amplified submarine systems

The advent of erbium doped fibre amplifiers (EDFA) has revolutionised the options available to submarine cable system planners. It has become possible to extend the range of unrepeatered systems operating at 1.55 μm to about 300-400 km. The next generation of optical systems, TAT12/13 and TPC5, which are planned for the Atlantic and Pacific Oceans in 1995/6 will use optical amplifiers and operate at 5 Gbit/s per fibre pair. The authors look at constraints on the operation of long haul optically amplified systems and suggest areas where progress needs to be made in order to allow operation at rates beyond 5 Gbit/s. Gordon-Haus jitter and provision of an adequate SNR have been recognised as the limiting factors for soliton systems. However, guiding filters may allow these constraints to be relaxed and higher speed operation achieved. Soliton systems may also offer the promise of multi-channel operation using either two polarisation states or a few WDM channels. The latter requires that the gain of each wavelength channel can be adequately controlled