Seabed Optical Fiber Cable for Water Pressure Fluctuation Detection
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Solution Overview
Problem
Existing methods struggle to detect slow and slight movements of the ground, such as crustal deformation, using optical fiber sensors, and face challenges in efficiently measuring water pressure fluctuations in offshore environments.
Innovation Solution
A water pressure fluctuation measuring system utilizing a cable with a first optical fiber installed on the seabed, equipped with partial reflection units, which measures length changes based on round-trip propagation time of reflection light to monitor ground movements and pressure fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If optical fiber sensors are used to detect ground movement, then the monitoring coverage is improved, but the ability to detect slow and slight movements such as crustal deformation deteriorates
Solution Approach 1:
The optical fiber cable is divided into multiple sections with discrete reflection units at specific positions. Each reflection unit acts as an independent measurement point, allowing the system to monitor multiple locations simultaneously while maintaining high detection precision for slow movements like crustal deformation through cumulative length changes of optical fiber sections.
Solution Approach 2:
Reflection units are introduced as intermediary elements within the optical fiber cable. These units reflect light back to the measurement device, enabling precise detection of optical fiber length changes. The reflection units serve as mediators that convert subtle ground movements into measurable optical signal variations, significantly improving the detection capability for slow and slight movements.
2Measurement precision
If multiple reflection units are provided in the optical fiber cable, then the measurement precision of water pressure fluctuations is improved, but the device complexity increases
Solution Approach 1:
Multiple reflection units are integrated into a single optical fiber cable, merging multiple measurement functions into one unified structure. The cable simultaneously performs both communication and sensing functions, with reflection units at different positions enabling multiple measurement points along the cable path, thereby improving measurement precision without requiring separate sensing systems.
Solution Approach 2:
The optical fiber cable serves multiple functions: it acts as both a communication transmission medium and a sensing element for water pressure fluctuation detection. The reflection units enable the cable to function as a distributed sensor array, allowing a single cable structure to perform both its traditional communication role and the additional function of precise environmental monitoring.
3Difficulty of detecting and measuring
If OTDR is used to measure optical fiber length changes, then the detection capability is improved, but the loss of time due to measurement processing increases
Solution Approach 1:
The OTDR measurement is performed periodically at predetermined time intervals rather than continuously. This periodic measurement approach maintains the ability to detect optical fiber length changes accurately while reducing the overall measurement processing time and data processing burden, as the system only needs to perform measurements at specific intervals rather than continuously monitoring.
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 accurate detection of water pressure fluctuations and ground movements, providing high-resolution monitoring with reduced environmental interference and improved economic efficiency.
Implementation Method 1
a partial reflection unit provided on a path of the first optical fiber in the cable and configured to partially reflect the monitoring light
Implementation Method 2
an optical output unit configured to output monitoring light to the first optical fiber
Implementation Method 3
an optical reception unit configured to receive reflection light reflected by the partial reflection unit
Data Source
AI summary
A water pressure fluctuation measuring system detects a water pressure fluctuation. A cable, which includes an optical fiber, is provided on or in the ground of the seabed in such a way that the optical fiber is expanded and contracted according to the water pressure fluctuation. An optical output unit outputs 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 reflection light reflected by the partial reflection unit. A calculation unit measures a length of the optical fiber to the partial reflection unit, based on a round-trip propagation time of the received reflection light, and monitors a change of the length over time.