Fault-Tolerant Fiber Optic Intrusion Detection
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Solution Overview
Problem
Fiber-optic intrusion detection systems are vulnerable to interruptions and unable to detect or report breaks in the sensing optical fiber, which hinders their deployment in critical security applications.
Innovation Solution
The implementation of optical time domain reflectometry (OTDR) with redundant signal processing circuitry at both ends of the optical fiber to analyze backscatter signals, detect intrusions, identify and locate breaks, and output alarms, ensuring continuous operation and reporting of fiber breaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single optical fiber is used for intrusion detection, then the system structure is simple, but the system reliability deteriorates because a break completely disables the system
Solution Approach 1:
The optical fiber sensing system is segmented into multiple independent sensing sections, each monitored by OTDR from both ends. This segmentation allows the system to isolate and continue monitoring unaffected sections even when a break occurs in one section.
Solution Approach 2:
The system transitions from single-end monitoring to dual-end monitoring, adding a spatial dimension to the monitoring approach. By placing OTDR instruments at both ends of the optical fiber and analyzing backscatter signals from both directions, the system achieves fault tolerance without significantly increasing overall complexity.
2Ease of operation
If traditional fiber optic intrusion detection systems are used, then the system is easy to operate, but the system cannot detect or report break locations
Solution Approach 1:
The OTDR system provides continuous feedback by analyzing backscatter signals to detect and locate fiber breaks. The system automatically generates location information for breaks and provides this feedback to operators, enabling informed decision-making without complicating operation.
Solution Approach 2:
The system performs self-diagnosis by automatically detecting and locating fiber breaks through OTDR analysis of backscatter signals. This self-service capability provides break location information without requiring additional manual inspection or complex operational procedures.
3Reliability
If redundant OTDR systems are implemented at both ends of the fiber, then the reliability improves, but the device complexity increases
Solution Approach 1:
The OTDR system at each end serves multiple functions: monitoring intrusions in its respective direction and detecting breaks anywhere in the fiber. This multi-functionality allows redundant monitoring capability without proportionally increasing complexity, as each OTDR unit performs comprehensive monitoring tasks.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables continuous operation and accurate reporting of fiber breaks, enhancing the reliability and effectiveness of fiber-optic intrusion detection systems for various security applications.
Implementation Method 1
the OTDR means includes first signal processing circuitry that analyzes the backscatter signal received via the first end of the at least one optical fiber
Data Source
AI summary
An intrusion detection system for monitoring a premises includes at least one optical cable that houses at least one optical fiber and extends about the premises. Optical time domain reflectometry (OTDR) means is operably coupled to opposite first and second ends of the at least one optical fiber. The OTDR means includes first signal processing circuitry that analyzes the backscatter signal received via the first end of the at least one optical fiber in order to detect an intrusion of the premises, and second signal processing circuitry that analyzes the backscatter signal received via the second end of the at least one optical fiber in order to detect an intrusion of the premises. The redundancy of intrusions decisions made by the first and second signal processing circuitry can be verified. The system preferably further includes means for detecting a break in the at least one fiber, for identifying location of the break, for outputting to a user the location of the break, and for raising an alarm indicating the break.