Secured fiber link system

A secured fiber link system, comprising:

• a spatially multiplexing optical fiber, the spatially multiplexing optical fiber being a multicore fiber;
• a transmit spatial multiplexer configured to couple each of a plurality of optical signals into a respective one of a plurality of distinct spatial paths of the spatially multiplexing optical fiber, each of the spatial paths being able to carry an optical signal;
• at least one optically modulated transmit source coupled to the transmit spatial multiplexer so that an optically modulated signal supplied as an output from the at least one optically modulated transmit source is coupled by the transmit spatial multiplexer into one of the plurality of spatial paths of the spatially multiplexing optical fiber, the one of the plurality of spatial paths of the spatially multiplexing optical fiber being a center core of the multicore fiber;
• at least one optically modulated chaff source coupled to the transmit spatial multiplexer so that each optically modulated chaff signal supplied as an output from the at least one optically modulated chaff source is coupled by the transmit spatial multiplexer into a respective one of the plurality of spatial paths of the spatially multiplexing optical fiber that are other than the spatial path to which the at least one optically modulated transmit source is coupled, each of the spatial paths of the spatially multiplexing optical fiber that are other than the spatial path to which the at least one optically modulated transmit source is coupled being a non-central core of the multicore fiber, wherein at least one of the at least one optically modulated chaff source occupies substantially a same optical frequency range as at least one of the at least one optically modulated transmit source;
• and
• a receive spatial multiplexer configured to extract the optical signal carried on at least one of the spatial paths of the spatially multiplexing fiber, wherein the at least one spatial path from which the optical signal is extracted includes at least the center core of the multicore fiber, wherein the at least one extracted optical signal is detected locally, and wherein the at least one extracted optical signal is made available as a system output;
• wherein a power of the at least one optical chaff signal and a power of the at least one transmit signal are measured, and wherein a ratio of the measured optical chaff and transmit signal powers are compared at the receive spatial multiplexer to a ratio of at least one optical chaff signal power and at least one transmit signal power as measured at the transmit spatial multiplexer.