A method and apparatus for securing an optical communication link includes
the step of identifying a profile of the link by measuring, at the
transmitter, optical back-reflections from optical pulses forwarded to a
receiver. The profile is stored at the transmitter. Periodically during
operation, such as during key exchange, more optical pulses are forwarded
to the receiver, and the back reflections are collected as periodic
profiles. The periodic profiles are compared against the stored profiles.
Eavesdroppers, such as those who cut the fiber, tap the fiber, or
implement a man in the middle attack, may be easily identified because
the losses caused by their interference with the fiber will be evident in
the periodic profiles.