Multimode Fiber Intrusion Detection for Single Mode Networks
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Solution Overview
Problem
In a single fiber multi-drop security system, the combination of multiple optical signals of the same wavelength causes instability and interference, making standard detection methods ineffective due to wild fluctuations from slight disturbances in the fiber.
Innovation Solution
Injecting the combined single-mode optical signals into a multimode fiber, where they are analyzed using multimode speckle detection methods or by transferring the signal to a single-mode fiber to detect variations in modal distribution, allowing for effective intrusion detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple optical signals of the same wavelength are combined in a single fiber, then fiber resource utilization is improved, but signal stability deteriorates due to interference and wild fluctuations
Solution Approach 1:
The patent introduces a multimode fiber as an intermediary component between the single-mode fiber network and the detection system. The multimode fiber receives combined single-mode signals and converts them into a multimode signal format, which then can be analyzed using speckle detection methods. This intermediary conversion resolves the contradiction by enabling stable detection of combined signals that would otherwise be unstable due to wavelength interference.
Solution Approach 2:
The patent changes the optical mode parameter by transferring signals from single-mode to multimode fiber. This parameter change transforms the signal characteristics, allowing the use of speckle detection techniques that are sensitive to fiber movement while being immune to wavelength interference issues. The mode distribution change enables stable intrusion detection despite signal combination.
2Device complexity
If standard detection methods are used on combined signals, then detection simplicity is maintained, but detection accuracy deteriorates due to wild fluctuations from fiber disturbances
Solution Approach 1:
The multimode fiber acts as a mediator that translates combined single-mode signals into a format suitable for speckle detection. This intermediary conversion enables the use of simple detection methods while achieving high accuracy, as the multimode signal's speckle pattern is sensitive to fiber movement but not to wavelength interference.
Solution Approach 2:
The patent replaces traditional mechanical or electronic detection methods with optical speckle detection. By using the optical properties of multimode fibers and analyzing speckle pattern changes, the system achieves high measurement precision without complex mechanical sensing mechanisms, substituting a simpler optical detection approach for more complex systems.
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
This approach enables reliable detection of fiber movement and potential intrusions by stabilizing signal analysis and reducing false alarms, suitable for both single fiber and PON systems.
Implementation Method 1
the light signal in the single mode fiber are analyzed by injecting the signals from the single mode fiber into a multimode fiber and analyzing changes in a signal from the multimode fiber
Implementation Method 2
transmitting through the fibers a signal which can be analyzed for changes in its characteristics which are indicative of movement as a prelude to an intrusion event
Data Source
AI summary
A method is provided for detecting intrusion into an optical cable of a single mode optical fiber network comprising where monitoring light signals are transmitted along a telecommunications optical fiber to be monitored either along a fiber additional to a data fiber or by multiplexing onto a common fiber. The received monitoring light signals after transmission along the telecommunications optical fiber are analyzed for changes indicative of movement of the optical fiber for detecting an intrusion event. The monitoring light signals at the receive end of the fiber signals are monitored by feeding the signals from the single mode fiber into a multi-mode fiber in a manner which causes changes in modal power distribution which can be detected by taking a portion only of the modes.