Seismic Detection Using Optical Fiber Stokes Parameters
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Solution Overview
Problem
Sparse seismic instrumentation in oceans limits earthquake detection capabilities, with many underwater earthquakes going undetected due to the distance from land-based seismic stations, and tsunami detection equipment being suboptimal for generating timely warnings.
Innovation Solution
An optical communication system that repurposes existing fiber-optic cables to function as earthquake sensors by transmitting optical-probe signals and using coherent optical receivers to measure Stokes parameters, allowing for the determination of earthquake epicenters and tsunami forecasts based on seismic disturbances detected in the cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If land-based seismic stations are used for earthquake detection, then detection capability is limited to areas near land, but coverage of underwater earthquakes is insufficient
Solution Approach 1:
The patent repurposes existing submarine optical communication fibers to serve dual functions: data transmission and seismic detection. By integrating seismic sensing capability into the communication infrastructure, the system achieves both universal communication and earthquake detection without requiring separate instrumentation, thereby expanding detection coverage to ocean areas while maintaining detection accuracy through specialized signal processing of polarization state changes.
2Measurement precision
If traditional seismic instrumentation is deployed in oceans, then earthquake detection capability improves, but cost and infrastructure complexity increase significantly
Solution Approach 1:
The patent makes existing submarine communication fibers perform dual functions as both data transmission medium and seismic sensor, eliminating the need for separate ocean-bottom seismograph deployments. This multi-functional approach maintains high detection accuracy while dramatically reducing infrastructure complexity and deployment costs.
Solution Approach 2:
The system utilizes the existing optical communication infrastructure to provide seismic detection services. The communication fibers themselves serve as the sensing element, detecting seismic waves through polarization state changes without requiring external sensing equipment, thereby making the infrastructure self-sufficient for both communication and monitoring purposes.
3Measurement precision
If existing fiber-optic cables are modified for seismic detection, then detection capability is achieved, but network equipment complexity increases
Solution Approach 1:
The patent replaces traditional mechanical seismic sensors with an optical detection system that measures polarization state changes of light propagating through the fiber. This substitution eliminates mechanical moving parts and complex sensor assemblies, achieving high detection accuracy while actually simplifying the overall system architecture through non-contact, all-optical measurement techniques.
4Area of stationary object
If more seismic stations are deployed to improve coverage, then detection capability increases, but cost and maintenance requirements increase
Solution Approach 1:
The patent enables each submarine optical fiber to serve as both a communication channel and a seismic sensor, allowing a single infrastructure element to perform multiple functions. This eliminates the need to deploy additional separate seismic instruments, achieving expanded detection coverage without increasing the quantity of specialized sensing equipment.
Solution Approach 2:
The system merges the communication function and seismic sensing function into a single integrated infrastructure. By combining these previously separate functions into the optical fiber itself, the system achieves broad detection coverage using the existing communication network rather than requiring additional standalone seismic stations.
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 and characterization of earthquakes and prediction of tsunami waves with minimal additional cost and infrastructure modifications, improving detection capabilities and warning times for coastal communities.
Implementation Method 1
a low-complexity, low-latency coherent optical receiver is used to obtain time-resolved measurements of the Stokes parameters of the optical-probe signal. The signal-processing chain of the optical receiver employs digital filtering to select frequency components of the measurements streams corresponding to seismic disturbances of the fiber-optical cable
Implementation Method 2
a low-complexity, low-latency coherent optical receiver is used to obtain time-resolved measurements of the Stokes parameters of the optical-probe signal
Data Source
AI summary
An optical communication system that enables any deployed fiber-optic cable to function as an earthquake-detection sensor. In an example embodiment, a WDM optical transmitter of one network node operates to transmit a CW optical signal together with legacy data-carrying optical signals. At another network node, a low-complexity, low-latency coherent optical receiver is used to obtain time-resolved measurements of the Stokes parameters of the CW optical signal. The signal-processing chain of the optical receiver employs digital filtering to select frequency components of the measurements streams corresponding to seismic disturbances of the fiber-optical cable connecting the nodes. The selected frequency components are then used to compute values of an earthquake indicator, which are reported to a network controller. Based on such reports from three or more nodes, the network controller can determine the epicenter and magnitude of the earthquake and, if warranted, may generate a tsunami forecast.