Diagram (from http://en.m.wikipedia.org/wiki/File:Jimmy_Carter_Front.jpg ) of USS Jimmy Carter indicating some additions to aid a cable listening mission (click on image to expand).
Vigilis at Molten Eagle wrote the following excellent post on July 3, 2013, see http://aquilinefocus.blogspot.com.au/2013/07/article-ties-uss-jimmy-carter-ssn-23-to.html :
"Article ties USS Jimmy Carter (SSN 23) to 'Sensitive' NSA ListeningBackground
Tamedia Publications romandes http://www.linkedin.com/company/tamedia-publications-romandes * SA is a Swiss media group headquartered in Zurich. With daily and weekly newspapers, magazines, and newspaper printing part sof Tamedia media companies. The company was founded in 1893 and is listed on the Swiss Stock Exchange since 2000.
*Suisse romande or Romandie refers to French-speaking districts of western Switzerland. "Suisse romand" describes the French dialect spoken in Switzerland.
July 7, 2013 Tribune de Genève L'USS Jimmy Carter, les oreilles de la NSA au fond des mers - By Pascal Schmuck.
Translated excerpts [emphasis mine]: The USS Jimmy Carter, the ears of the NSA on the seabed
The particular American nuclear sub is capable of monitoring submarine optical fiber cables. No communication seems immune to the ears of the National Security Agency (NSA). Satellite comms are routinely monitored by the Echelon program, but the fiber optic submarine cables have not escapes their monitoring.
Of course, transatlantic comms are already monitored on both sides of the ocean, by the Americans and the British. But the United States has also developed a special nuclear submarine capable of intercepting more sensitive communications. The USS Jimmy Carter was built in the early 2000s to operate wiretaps.
Since we know that almost 90% of Internet traffic is carried by submarine cable versus 10% by satellite. Submarine cables give rise to many fantasies, as we hear whenever one of them is cut. USS Jimmy Carter seems to represent a capability of strategic significance.********
NOTES (Wikipedia)1- As of 2006, overseas satellite links accounted for only 1 percent of international traffic, while the remainder was carried by undersea cable .
2- [USS Jimmy] Carter has additional maneuvering devices fitted fore and aft that will allow her to keep station over selected targets in odd currents. Past submarines outfitted this way were used to tap undersea cables, to intercept communications of foreign countries. Intelligence experts speculate that the MMP may find use in similar missions as an underwater splicing chamber for fiber optic cables.Submarines are always silent and strange.