Optical Fiber Cable with Partial Reflection Units for Ground Movement Detection
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Solution Overview
Problem
Existing surveying methods, such as optical fiber sensors, are unable to detect slight and slow movements of the ground, like crustal deformation, due to limitations in monitoring changes in optical fiber length over long distances.
Innovation Solution
A surveying system that includes an optical fiber cable with a partial reflection unit, where the optical fiber is expanded and contracted with ground movement, and uses OTDR to measure the length changes based on round-trip propagation time of reflection light, allowing for monitoring of ground movement over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If optical fiber sensors are used to monitor ground movement, then the monitoring coverage can be extended, but the ability to detect slight and slow movements like crustal deformation deteriorates
Solution Approach 1:
The optical fiber cable is divided into multiple sections with reflection units positioned at specific intervals. Each section acts as an independent measurement segment, allowing the system to detect slight movements in each segment while covering a large overall area. The reflection units create discrete measurement points that can individually track minor displacements along the entire fiber length.
Solution Approach 2:
Reflection units are introduced as intermediary elements within the optical fiber cable. These units serve as mediators that enhance the detection of slight movements by creating measurable reflection signals. When the fiber expands or contracts due to ground movement, the reflection units provide distinct optical signatures that make subtle changes detectable, thus improving measurement precision without limiting coverage area.
2Length of stationary object
If the optical fiber cable is laid over long distances to monitor wide-range ground movement, then the coverage area increases, but the precision in measuring length changes deteriorates
Solution Approach 1:
The long optical fiber cable is segmented into multiple measurement sections by positioning reflection units at regular intervals. Each segment between reflection units functions as an independent measurement zone, allowing precise length change detection in each segment while the entire cable spans long distances. This segmentation enables the system to maintain high measurement precision across extended monitoring distances.
Solution Approach 2:
Instead of attempting to measure the entire long cable as a single unit, the system uses partial measurements at multiple discrete points defined by reflection units. By taking measurements at these distributed points along the cable length, the system achieves accurate length change detection for each segment, which collectively provides precise monitoring over the full long distance.
3Length of stationary object
If conventional OTDR is used to measure optical fiber length, then the measurement range can cover the entire fiber, but the precision for detecting slight length changes deteriorates
Solution Approach 1:
Reflection units are introduced as intermediary elements that enhance the OTDR measurement capability. These units create strong, distinct reflection signals at specific positions along the fiber, serving as reference markers that improve the precision of length change detection. The reflection units act as mediators between the OTDR system and the fiber, enabling the detection of slight length changes that would otherwise be undetectable over long measurement ranges.
Solution Approach 2:
The system utilizes changes in optical reflection characteristics (analogous to color changes) to detect length variations. When the optical fiber undergoes slight length changes due to ground movement, the position and intensity of reflections from the reflection units change. By monitoring these optical signal variations, the system can precisely detect minute length changes while maintaining the ability to measure across the entire long fiber length.
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 the detection of slight ground movements by accurately measuring changes in the optical fiber length, effectively addressing the limitations of previous technologies in monitoring slow and wide-range ground movements.
Implementation Method 1
a cable that includes a first optical fiber and is provided so as to have friction between the cable and the ground, the cable being provided in such a manner that the first optical fiber is expanded and contracted in accordance with a movement of the ground
Implementation Method 2
a partial reflection unit that is provided on a path of the first optical fiber in the cable and partially reflects the monitoring light
Implementation Method 3
an optical output unit configured to output a monitoring light to the first optical fiber; an optical reception unit configured to receive a reflection light reflected by the partial reflection unit; and a calculation unit configured to measure the length of the first optical fiber to the partial reflection unit based on a round-trip propagation time of the reflection light
Data Source
AI summary
A slight movement of the ground is detected. A cable, which includes an optical fiber, is provided to have friction with the ground in such a way that the optical fiber is expanded and contracted in accordance with the movement of the ground. An optical output unit outputs a monitoring light to the optical fiber. A partial reflection unit is provided on a path of the optical fiber in the cable and partially reflects the monitoring light. An optical reception unit receives a reflection light reflected by the partial reflection unit. A calculation unit measures the length of the optical fiber to the partial reflection unit based on a round-trip propagation time of the reflection light that has been received and monitors its changes over time.