Locally nulled sine-wave total power alarm for intrusion detecting optical communications systems
AssigneeThe United States of America as represented by the Director, National Security Agency
InventorHarvey E. Solomon
Life of this patent
Estimating the term…
Abstract
An intrusion detection optical communication system modifies the original data signal to include a synchronizing periodic waveform. The receiver generates an inverted synchronizing periodic waveform signal corresponding with the transmitted signal to null the same under normal operation. When an intrusion in the optical system arises, power is extracted from the system and the nulled condition is disrupted. The disruption is detected and activates an alarm circuit when the disruption is above a threshold value.
Claims15
An intrusion detection optical system, comprising
- (a) first means for generating a combined multiplexed data and periodic subcarrier alarm waveform optical signal;
- (b) optical fiber means connected with said first generating means for transmitting said combined signal;
- and
- (c) means connected with said optical fiber means for receiving said combined signal, said receiving means including
- (1) second means for generating a local optical signal including a periodic wave component matched with the periodic subcarrier alarm waveform of said transmitted combined signal;
- (2) means for combining said transmitted and local optical signals to produce a composite output signal;
- (3) filter means connected with said combining means for passing only non-zero periodic wave components from said composite output signal;
- and
- (4) means connected with said filter means for detecting and indicating the presence of non-zero periodic wave components above a threshold value as a result of an intrusion into said optical fiber means.
A method for detecting intrusions in an optical communication system, comprising the steps of
- (a) generating a combined multiplexed data and periodic subcarrier alarm waveform optical signal;
- (b) transmitting said combined signal;
- (c) demultiplexing said transmitted combined signal at a receiver to extract the data therefrom;
- (d) generating a feedback periodic waveform optical signal within said receiver corresponding with said transmitted periodic waveform optical signal;
- (e) combining said feedback and transmitted periodic waveform to obtain a normally nulled waveform condition;
- and
- (f) detecting a disruption from said normally nulled waveform condition above a threshold value as a result of an intrusion into the optical communication system.
Dependencies are inferred from the claim text.