Distributed Fiber Optic Sensing: Principle and Application
Distributed Fiber Optic Sensing (DFOS) is a revolutionary technology that utilizes a standard optical fiber simultaneously as both a transmission medium and a continuous, distributed sensor. It enables real-time, precise detection of subtle changes along the entire length of the fiber, making it the "perceptual neural network" for building an intelligent world.
The diagram below intuitively illustrates the core principle and technical branches:
Core Technical Principles
The foundation of DFOS lies in three primary types of backscattered light generated as light propagates through the fiber. Each type is sensitive to specific physical parameters:
- Rayleigh Scattering: This is the strongest backscattered signal. External vibrations or acoustic waves acting on the fiber alter the phase or intensity of the Rayleigh backscattered light. By detecting these changes (e.g., using Phase-Sensitive Optical Time Domain Reflectometry, φ-OTDR), highly sensitive vibration and acoustic wave monitoring can be achieved.
- Raman Scattering: This is an inelastic scattering phenomenon that is extremely sensitive to temperature. The system precisely calculates the temperature at each point along the fiber by analyzing the intensity ratio of the backscattered anti-Stokes light to Stokes light. This mature technology is the foundation of Distributed Temperature Sensing (DTS).
- Brillouin Scattering: Another type of inelastic scattering, the resulting Brillouin frequency shift is linearly related to both the strain and temperature experienced by the fiber. Therefore, by detecting the frequency shift, high-precision distributed measurement of strain and temperature is possible, making it a core technology for monitoring deformation in large structures.
By measuring the return time of the scattered signals, the system can accurately locate the position of events, enabling a "CT scan" of the entire fiber.
Key Application Scenarios
Leveraging its unique advantages—immunity to electromagnetic interference, corrosion resistance, long-distance coverage, and passive monitoring—DFOS has become the "guardian" for safety monitoring of critical infrastructure.
|
Application Area |
Typical Scenarios & Technologies |
Practical Value |
|
Energy & Power |
Oil/gas pipeline leak detection (DAS), High-voltage cable/overhead line ice and temperature monitoring (DTS/BOTDR) |
Early warning of third-party damage or geological hazards, preventing major safety incidents and energy supply disruptions. |
|
Infrastructure |
Bridge/tunnel deformation monitoring (BOTDA), High-speed railway track structural health monitoring |
Enables millimeter-level deformation monitoring, providing crucial data for structural safety assessment and maintenance decisions. |
|
Public Safety |
Border/airport perimeter security (DAS), Leak detection for urban underground pipelines (water, gas) |
Provides meter-level precision for intrusion and leak location with a very low false alarm rate, significantly improving emergency response efficiency. |
|
Geology & Oceanography |
Landslide early warning, seismic wave monitoring, Submarine fiber-optic cable seismic observation (DAS) |
Creates high-density, low-cost seismic observation networks, capturing precursor signals of geological disasters in real time. |
Future Development Trends
Currently, DFOS technology is advancing towards longer distances, higher precision, multi-parameter integration, and intelligence. Recent research has achieved 100 km sensing distances while maintaining 1-meter spatial resolution, with stable operation in extreme environments like high radiation and high temperature. Concurrently, integrating deep learning and other artificial intelligence algorithms allows systems to automatically identify and classify different disturbance events (e.g., distinguishing between an excavator, a pedestrian, or a vehicle) from massive data with over 95% accuracy, significantly enhancing the intelligence level of monitoring systems.
Shenzhen Fholink Technology Co., Ltd. , in response to market developments, has launched integrated DVS modules, integrated DAS modules, and integrated DTS modules to meet the needs of different customers. Both new and existing customers are welcome to inquire!
