What is "Photosensitive Fiber"?

International Zone (English) OFSCN Knowledge Base (Public)
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Can a grating be inscribed into just any standard broadband fiber used for home internet?

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No, a fiber Bragg grating (FBG) cannot be effectively inscribed into just any standard broadband fiber (such as standard G.652 single-mode fiber used for home internet) under normal conditions.

To understand why, we must look at the physical principles of Photosensitivity and the manufacturing process of FBGs:

1. The Requirement of Photosensitivity

Fiber Bragg gratings are typically inscribed using ultraviolet (UV) light to create a periodic variation in the refractive index of the fiber core. Standard communication fibers are designed for low loss and high bandwidth, not for photosensitivity.

  • Doping: Photosensitive fibers are specially doped with Germanium (Ge) at higher concentrations than standard fibers. When exposed to UV light, the Germanium-Oxygen bonds in the glass matrix break and rearrange, causing a permanent change in the refractive index.
  • Standard Fiber Limitation: The Germanium content in standard broadband fiber is generally too low to allow for a significant refractive index change through UV exposure alone.

2. Specialized Pre-treatments

While it is technically possible to make standard fiber “photosensitive” through a process called Hydrogen Loading (soaking the fiber in high-pressure hydrogen gas for several days), this is a complex industrial process. Even then, the resulting gratings are often less stable and more prone to “fading” over time compared to those inscribed in dedicated photosensitive fibers.

3. OFSCN® Solutions

For high-quality FBG sensing, we utilize specialized fibers that ensure long-term stability and high reflectivity. For example, our sensors utilize various specialized fibers depending on the environment:

In summary: While standard telecommunication fiber is excellent for data, it lacks the chemical composition required for efficient grating inscription. Specialized Photosensitive Fiber is the industry standard for producing reliable FBG sensors.

If you are looking into FBGs for a specific sensing application, could you specify what physical parameter (e.g., temperature, strain) you are aiming to measure?