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Fiber tapping uses a network tap method that extracts signal from an optical fiber without breaking the connection. Tapping of optical fibre allows diverting some of the signal being transmitted in the core of the fibre into another fibre or a detector. Fibre to the home (FTTH) systems use beam splitters to allow many users to share one backbone fibre connecting to a central office, cutting the cost of each connection to the home. Test equipment can simply put a bend in the fibre and extract sufficient light to identify a fibre or determine if a signal is present. Similar techniques can surreptitiously tap fibre for surveillance, although this is rarely done where electronic equipment used in telecommunication is required to allow access to any phone line for tapping by legal authorization. Tapping the fibre means that all signals from every communications source being routed through the fibre are presented and must be sorted for relevant data, an immense task when thousands of sources of data or voice may be present. According to reports, tapping fibre was used by the US government for surveillance following the September 11, 2001 attacks and a nuclear submarine, the Jimmy Carter, was modified to allow tapping undersea cables. 〔(Jimmy Carter Super Spy ) defensetech.org〕 == Detecting fiber taps == One way to detect fiber tapping is by noting increased attenuation added at the point of tapping. There are, however, tappers which allow tapping without significant added attenuation. In either case there should be a change of scattering pattern in that point in line which, potentially, can be detectable. However once the tapper has been detected it may be too late since a part of the information has been already eavesdropped. See the NCS reference below for a more complete explanation. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fiber tapping」の詳細全文を読む スポンサード リンク
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