Application of the 40Gbps or 100Gbps technology to all the wavelengths on a fibre has the potential to increase capacity four or 10 fold from that of a 10Gbps system but Ryan Perera, head of metro ethernet networks for Nortel Asia. said that optical signal transmission limitations in the fibre, such as dispersion, would limit its application to about 20 percent of the wavelengths available for 10Gbps transmission.
Even so, such a means of achieving a significant increase of capacity on an existing system for much less cost than a new system could compromise the business case for new systems, or lead to a glut of capacity and subsequent price collapse.
According to Dean Veverka, VP operations for Southern Cross, "Nortel's technology gives us a simple, cost-effective upgrade to 40Gbps and an equally simple upgrade path to 100Gbps in the future. We are also looking at the potential for this 40Gbps technology to be deployed on our longer distance submarine segments.
The 40Gps product became generally available only six weeks ago but Nortel has already signed up 14 customers according to Perera. In Asia Nortel has seven trials underway and more planned. Veverka told iTWire that if the equipment performed successfully on the terrestrial component, Southern Cross would install it in one of the submarine links in its network - which comprises a figure of eight loop with two links from Australia to Hawaii via New Zealand and two from Hawaii to the US west coast.
Perera said that Nortel also had about five trials of the 100Gbps technology in place and was planning one soon with an Australian carrier. He was confident that the 40Gbps technology would be able to perform satisfactorily on the subsea component of the Southern Cross network, saying it was already in place on a South American cable network where it is carrying 40Gbps of traffic over distances of 4700kms.
According to Perera Nortel has been developing the technology for about six years, and it works by using a different modulation technique to encode the data onto the light signal. The technique, known as DP-QPSK is widely used in RF data transmission and Nortel has adapted it to the optical realm to encode data on four different planes of polarisation of the optical signal. Southern Cross, and many other long haul cables, use optical amplifiers not regenerators to boost the signal under the ocean and the 40Gbps signal is passed and amplified in exactly the same way as a 10Gbps signal.