Abstract

Transoceanic cable transmission systems are on the verge of a capacity increase, the magnitude of which has not been equaled since the change from analog coaxial cable to digital light-wave systems. The next generation of undersea cable transmission systems will use erbium-dopedfiber amplifiers (EDFAs) in the repeaters to boost signals periodically as they travel across the world's oceans. The first optical amplifier systems will increase the transmission capacity four to eight fold over the most advanced regenerator systems now in use today. The first generation of undersea optical amplifier systems will go into service in the 1995-1996 time frame. These systems will use the NRZ modulation format at bit rates up to 5 Gb/ s, with dispersion shifted fiber that is matched to the operating wavelength. The feasibility of this type of system has been demonstrated with circulating loop experiments with transmission distances in excess of 21,000 km and with long straight experiments of lengths up to 4500 km. The technique of measuring the bit error rate in a circulating loop, which we first reported one year ago, has proven to be quite useful in the design of long-haul optical amplifier systems. With this technique we have demonstrated transmission distances of 14,000 km and 21,000 km at 5 Gb/s and 2.4 Gb/s data rates for a maximum bit rate distance product of 71 Tb km/sec. These results showed that 5 Gb/s all-optical EDFA transmission systems are capable of achieving transoceanic distances at very low error rates.

© 1992 Optical Society of America