A system and method for securing communication over an optical fiber are disclosed. The system includes a transmit spatial multiplexer configured to couple optical signals into spatial paths of an optical fiber, a first of the plurality of optical signals is an optically modulated version of a desired sequence of information that is intended to be transferred over the optical fiber and it is coupled into a first of the spatial paths; a second one of the plurality of optical signals is an optical chaff signal and it is coupled into a second spatial path different from the first one, and a third optical signal is an optical signal for use by an optical time domain reflectometer (OTDR) that is coupled into one of the spatial paths of the optical fiber, whereby a tap along the fiber cannot determine the transmitted desired sequence of information.