Setting a new record

Scientists from Bell Labs have doubled the distance record for high-bandwidth, long-distance transmission by sending 2.56 terabits of information per second over a distance of 4000 kilometres.

Scientists from Bell Labs have doubled the distance record for high-bandwidth, long-distance transmission by sending 2.56 terabits (trillion bits) of information per second over a distance of 4000 kilometres (2500 miles). The previous transmission record was 1.60 terabits of information per second over 2000 kilometres (1250 miles).

A technical paper detailing the achievement was presented last Friday at the post-deadline session of the Optical Fiber Communications (OFC) conference in Anaheim, CA.

The ultra long-haul all-optical transmission record was achieved using a 64-channel dense wavelength division multiplexing (DWDM) system, where each channel carried information at 40 gigabits per second. The DWDM technique, invented at Bell Labs, makes it possible to send multiple streams of information down the same optical fibre.

The fibre optics spans used in the Bell Labs experiment were 100 kilometres (62.5 miles) in length, typical of terrestrial networks used by service providers today. The previous distance record for a 40 gigabits per second transmission experiment over 100-kilometer fibre spans was exactly half of the 4000 kilometres (2500 miles) distance record that the Bell Labs team achieved, and the team used 64 channels whereas the previous experiment had used 40 channels.

The transmission breakthrough was made possible using the differential phase shift keying (DPSK) method, a new coding scheme for high-capacity communications developed at Bell Labs. When coupled with other technologies – such as extended L-band amplifiers, Raman amplifiers, forward error correction and optimal dispersion compensation – DPSK allowed the research team to achieve error-free transmission over 4,000 kilometres (2500 miles) for all 64 channels, each of which had a signal of 40 gigabits per second.

On the web