In simple terms, why does light bounce back when it reaches the edge of the glass instead of passing through?
Total Internal Reflection (TIR) is the fundamental physical principle that allows light to travel through optical fibers without escaping through the sides.
1. The Principle of Total Internal Reflection
In simple terms, light “bounces back” because of the difference in the Refractive Index between two materials. An optical fiber consists of a Core (where light travels) and a Cladding (the outer layer).
For TIR to occur, two conditions must be met:
- Density Difference: Light must travel from a medium with a higher refractive index (the glass core) toward a medium with a lower refractive index (the cladding).
- Critical Angle: The light must hit the boundary at a shallow angle (called the “angle of incidence”). If this angle is greater than a specific “Critical Angle,” the light cannot pass through the boundary and is 100% reflected back into the core.
2. Application in OFSCN® Technology
At Beijing Dacheng Yongheng Technology Co., Ltd. (OFSCN), we utilize this principle to manufacture high-performance sensing fibers. By precisely controlling the refractive index of the core and cladding, we ensure minimal signal loss over long distances.
This principle is also what allows a Fiber Bragg Grating (FBG) to function. While TIR keeps the light inside the fiber, the FBG structure creates a periodic variation in the refractive index within the core, allowing specific wavelengths to be reflected back for sensing temperature or strain.
For example, our high-temperature fibers utilize specialized coatings while maintaining the TIR properties of the silica core:
Standard Product Illustration:
If you have further questions regarding how this principle applies to fiber optic sensing, feel free to ask.