Secured Fiber Link Spatial Multiplexing
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Solution Overview
Problem
Optical fiber cables are vulnerable to tapping through bending or stretching, which can lead to data theft, and existing detection methods like OTDRs have limitations such as 'dead zones' and the need for additional signals that can compromise security, especially in highly secure communications.
Innovation Solution
A system that uses spatial multiplexing to transmit a desired data signal, a chaff signal, and an OTDR signal through multiple paths in an optical fiber, making it difficult for taps to extract the data while allowing detection of tampering using the OTDR signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data encryption is implemented using AES, then data payload is secured, but IP header information remains exposed revealing source and destination
Solution Approach 1:
The patent applies chaff signals to convert the harmful effect of header information exposure into a beneficial security mechanism. By injecting decoy signals that mimic legitimate traffic patterns, the system makes it difficult for attackers to distinguish real data from fake signals, thereby protecting information flow without modifying encryption protocols
2Measurement precision
If OTDR is used to detect fiber tapping, then tampering can be detected, but dead zones prevent detection of faults near the launch end
Solution Approach 1:
The patent resolves the dead zone limitation by transitioning from a single-launch-point measurement approach to a bidirectional measurement system. By placing OTDR instruments at both ends of the fiber link and analyzing reflections from both directions, the system eliminates blind spots and achieves complete coverage of the entire fiber length, including areas previously undetectable
3Ease of manufacture
If fiber bending or stretching is used for tapping, then data extraction is easy and effective, but detection is difficult
Solution Approach 1:
The patent implements continuous real-time monitoring using bidirectional OTDR measurements that provide immediate feedback on fiber integrity. Any physical disturbance such as bending or stretching causes detectable changes in reflection patterns, allowing the system to identify and locate tapping attempts as they occur rather than discovering them after the fact
4Reliability
If secure communication requirements prevent signal modification, then security is maintained, but OTDR testing cannot be performed on the same fiber
Solution Approach 1:
The patent segments the optical signal spectrum by allocating different wavelength channels for different purposes. Secure data communication occupies certain wavelength bands while OTDR testing operates on separate, dedicated wavelength channels. This spectral segmentation allows both secure communication and fiber testing to coexist on the same physical fiber without interfering with each other or compromising security
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
The system effectively secures communication by overwhelming taps with interfering signal energy and enabling detection of tampering, ensuring data integrity and security without modifying the secure data signal and reducing the need for additional equipment or encryption.
Implementation Method 1
a transmit spatial multiplexer configured to couple ones of a plurality of optical signals into ones of a plurality of spatial paths of an optical fiber
Implementation Method 2
A transmit spatial multiplexer couples ones of a plurality of optical signals into ones of a plurality of spatial paths of an optical fiber... wherein at least a second one of the plurality of optical signals is an optical chaff signal
Implementation Method 3
An OTDR typically operates by sending laser pulses of different widths and monitoring their refection as received at the pulse-transmitting end of the fiber
Data Source
AI summary
A system and method for securing communication over an optical fiber are disclosed. The system includes a transmit spatial multiplexer configured to couple optical signals into spatial paths of an optical fiber, a first of the plurality of optical signals is an optically modulated version of a desired sequence of information that is intended to be transferred over the optical fiber and it is coupled into a first of the spatial paths; a second one of the plurality of optical signals is an optical chaff signal and it is coupled into a second spatial path different from the first one, and a third optical signal is an optical signal for use by an optical time domain reflectometer (OTDR) that is coupled into one of the spatial paths of the optical fiber, whereby a tap along the fiber cannot determine the transmitted desired sequence of information.