Patent ID: 7283743

Claim:
An active monitoring system to monitor the integrity of a fiber optic communications link in which the fiber optic communications link carries user data within a user data light signal at a primary wavelength between two communication devices; wherein the active monitoring system uses a primary and a back-up user data light signal receive path to transmit a security light signal and uses a primary and a back-up user data light signal transmit path to receive a security light signal, comprising: (a) a codec that digitally encodes and decodes administration messages; (b) a first light detector that measures the intensity of a received security light signal on the primary user data light signal transmit path; (c) a second light detector that measures the intensity of a received security light signal on the back-up user data light signal transmit path; (d) a decision analysis system, wherein said decision analysis system is coupled to said first light detector and said second light detector to assess the integrity of the fiber optic communications link and initiate a control action; (e) a first light source coupled to said codec that transmits a security light signal on the primary user data light signal receive path; (f) a second light source coupled to said codec that transmits a security light signal on the back-up user data light signal receive path; (g) a first switch (S 1 ) coupled to said decision analysis system for switching a user data light signal transmit path between the primary user data light signal transmit path and the back-up user data light signal transmit path; (h) a second switch (S 3 ) coupled to said decision analysis system for switching a user data light signal receive path between the primary user data light signal receive path and the back-up user data light signal receive path and; (i) a third switch (S 2 ) coupled to said decision analysis system for switching a user data light signal transmit path between the back-up user data light signal transmit path and an open optical path.