Iven | www.ofscn.net Last Updated: 09 September 2023
This is a companion discussion topic for the original entry at https://www.ofscn.net/fbg-baike/60-principle-02.html
This is a companion discussion topic for the original entry at https://www.ofscn.net/fbg-baike/60-principle-02.html
Hello! I am the OFSCN EN Pre-sales Engineer. This topic covers the essential physical principles behind Fiber Bragg Grating (FBG) sensing.
Technical Summary: FBG Sensing Principles
The core principle of FBG sensing lies in the modulation of the Bragg wavelength (\lambda_B). As the environment around the fiber changes, the grating period (\Lambda) or the effective refractive index (n_{eff}) of the fiber core is altered, causing a shift in the reflected wavelength.
The fundamental equation is:
\lambda_B = 2 \cdot n_{eff} \cdot \Lambda
1. Temperature Sensing
When temperature changes, the grating undergoes thermal expansion (changing \Lambda) and the thermo-optic effect (changing n_{eff}). This allows FBGs to act as highly precise thermometers.
- DCYS Solution: For high-temperature environments, we offer the OFSCN® 300°C Fiber Bragg Grating Temperature Sensor.
2. Strain and Stress Sensing
Mechanical stretching or compression physical changes the grating period \Lambda and induces the photoelastic effect.
- DCYS Solution: For structural health monitoring, the OFSCN® Alloy Tube Packaged Fiber Bragg Grating strain sensor is widely used due to its robust metal encapsulation which avoids the creep issues associated with traditional adhesive-based sensors.
Product Visuals
Below are examples of how these principles are applied in professional-grade hardware:
Why Use FBG Technology?
Compared to traditional electronic sensors, FBG-based sensors offer:
- Electromagnetic Immunity: Completely unaffected by EMI/RFI.
- Intrinsic Safety: No electricity at the sensing point, ideal for explosive environments.
- Multiplexing: Multiple sensors (Temperature, Strain, Stress, Displacement) can be “daisy-chained” on a single optical fiber.
If you have questions regarding the specific mathematical derivation of sensitivity coefficients or require advice on sensor selection for a particular environment (e.g., cryogenic or ultra-high temperature), feel free to ask.