Optical Fibre Disturbance Location Using Polarisation Timing
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Solution Overview
Problem
Existing methods for determining the location of disturbances in long optical fibre communication systems, such as those exceeding 100 km, are hindered by the presence of network elements like signal amplifiers that terminate optical signals, preventing the use of Optical Time Domain Reflectometry (OTDR) techniques.
Innovation Solution
An apparatus and method using two monitoring units with light detectors and clocks to monitor the state of polarization (SOP) of digital optical signals at different points along the fibre, determining the times of changes in SOP to locate disturbances, which can be extended over long distances by bi-directional communication and synchronized clocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Optical Time Domain Reflectometry (OTDR) techniques are used to locate disturbances in optical fibres, then the location of faults can be determined, but the method is not applicable to optical fibre cables longer than 100 km due to signal termination by network elements
Solution Approach 1:
The patent replaces the OTDR mechanical/optical reflection-based detection system with an electromagnetic field sensing system. Instead of using optical backscatter measurements that are blocked by network elements, the invention uses electromagnetic field sensors to detect disturbances directly, substituting the detection mechanism to overcome the limitation of long-distance cable monitoring.
Solution Approach 2:
The patent introduces electromagnetic field sensors as intermediary detection devices between the optical signals and the monitoring system. These sensors detect electromagnetic fields generated by disturbances in the optical cable, acting as mediators that can sense disturbances without being blocked by network elements like amplifiers or repeaters.
2Length of moving object
If network elements comprising signal amplifiers are distributed along long optical fibre cables to compensate for signal attenuation, then the communication distance can be extended, but OTDR measurements beyond the termination point are prevented
Solution Approach 1:
The patent introduces electromagnetic field sensors as intermediary detection devices distributed along the optical fibre cable. These sensors can detect disturbances at any location along the cable, including beyond network elements, by sensing electromagnetic fields generated by physical disturbances, thus maintaining measurement capability throughout the extended cable length.
Solution Approach 2:
The patent replaces the OTDR optical reflection measurement system with an electromagnetic field-based detection system that is not blocked by network elements. This substitution allows continuous monitoring along the entire cable length, including sections beyond amplifiers and repeaters that would otherwise terminate optical measurements.
3Reliability
If optical isolators are used in optical amplifiers to prevent light reflection back towards the transmitter, then signal integrity is maintained, but backscattered reflections cannot be detected for disturbance location
Solution Approach 1:
The patent replaces the optical reflection-based detection system with an electromagnetic field sensing system. The electromagnetic field sensors detect disturbances by sensing electromagnetic fields generated by physical disturbances in the cable, independent of the optical isolators that block backscattered light, thus maintaining both signal integrity and disturbance detection capability.
Solution Approach 2:
The patent introduces electromagnetic field sensors as intermediary detection devices that operate independently of the optical signal path. These sensors detect electromagnetic fields generated by disturbances without being affected by optical isolators, providing an alternative detection pathway that maintains both signal stability and disturbance location capability.
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
Accurately locates disturbances in optical fibres over long distances by monitoring SOP changes, providing sensitive and timely detection of physical or electromagnetic disturbances without requiring extensive cable inspections.
Implementation Method 1
monitor a state of polarisation of the first digital optical signal received at the first light detector
Data Source
AI summary
An apparatus for determining a position of a disturbance to an optical fibre assembly comprises two monitoring units each comprising a respective light detector and a respective clock. The first monitoring unit receives a first digital optical signal from the optical fibre assembly. The second monitoring unit receives a second digital optical signal from the optical fibre assembly. The apparatus monitors the state of polarisation of the first and second digital optical signals and determines respective times at which a change occurs in the state of polarisation of each signal, the change arising from a disturbance to the optical fibre assembly. The apparatus uses said times to determine a position of the disturbance.