NEC and Tyco have started planning work on the Unity undersea fibre optic link between the US and Japan that's backed by Google and five telecom operators.

The $300m cable will initially contain five fibre pairs - dual optical fibre cables, one of which is used for service and the other for back-up - but will be expandable to eight pairs. Each pair is capable of carrying 960Gbps of data, giving the system a capacity of between 4.8Tbps and 7.68Tbps.

To put the Unity cable's capacity and growth in the transpacific cable market in perspective, TeleGeography said late last year that capacity in-use on transpacific cables stood at 3.3Tbps in total. Several cables are being upgraded to cope with increased demand and two new cables, Trans-Pacific Express and Asia America Gateway, should be online this year so total capacity is expected to be 7.2Tbps by the end of this year.

The cable is scheduled to come into use in the first quarter of 2010 at which time the owners predict further expansion in other cables will mean Unity will account for about 20 percent of capacity available across the Pacific.

In addition to Google, the other partners are India's Bharti Airtel; Malaysia's Global Transit; Japan's KDDI; and Singapore's Pacnet and SingTel.

Google's participation in the consortium made headlines when it was announced in February this year. Typically telecommunications carriers have been the only companies involved in building undersea fibre-optic cable systems, so Google's interest stood out from the other partners.