Secure optical communication components, method, and system

A secure subscriber loop optical communications system comprising:

• subscriber station set means for sending outgoing message and signaling information and receiving incoming message and signaling information;
• subscriber optical transmitter means having a message input, a signaling input, and a central office warning input and having a first secure optical output incorporating said outgoing information, and a first guard optical output for masking leakage of said first secure output;
• subscriber optical receiver means having a second secure optical input for said incoming information, and a second guard optical input, and having a message output, a signaling output, a subscriber alarm output and a central office warning output communicating to said central office warning input of said subscriber optical transmitter;
• subscriber system security status indication means responsive to said subscriber alarm output;
• station set line apparatus means for routing said outgoing message and signaling information from said station set to said message input and signaling input of said subscriber optical transmitter and routing said message output and said signaling output from said subscriber optical receiver as said incoming information to said station set;
• central office optical receiver means having a first secure optical input and a first guard optical input and having a central office message output, a central office signaling output, a subscriber warning output, and a central office alarm output;
• central office alarm indicator means responsive to said central office alarm output;
• central office optical transmitter means having a central office message input, a central office signaling input, and a subscriber warning input communicating with said subscriber warning output of said central office optical receiver, and having a second secure optical output for said incoming information and a second guard optical output capable of masking leakage of said second secure output;
• central office line apparatus means for routing said incoming message and signaling information from a central office line to said central office message input and central office signaling input of said central office optical transmitter and routing said central office message output and said central office signaling output from said central office optical receiver of said outgoing information to said central office line;
• and
• optical link means comprising first and second optical fiber transmission lines each having at least two cores encased in a cladding, including a central core surrounded by an opaque film in said cladding and also including at least one guard core exterior to said film;
• said central core and said guard core or cores of said first fiber connecting said first secure optical output and first guard optical output of said subscriber optical transmitter respectively to said first secure optical input and said first guard optical input of said central office optical receiver,
• said central core and guard core or cores of said second fiber connecting said second secure optical output and said second guard optical output of said central office optical transmitter respectively to said second secure optical input and said second guard optical input of said subscriber optical receiver, any said leakage from each said secure core through each said film of each said fiber being masked by each said guard signal output respectively;
• said first secure optical input and said first guard optical input being monitored by said central office optical receiver so as to produce said subscriber warning when tampering on said first fiber is detected, said second secure optical input and said second guard optical input being monitored by said subscriber optical receiver so as to produce said central office warning when tampering on said second fiber is detected;
• whereby a more secure subscriber loop is achieved.