Are these “markings” on the outside or the inside of the fiber? Also, will they make the fiber fragile or prone to breaking, similar to a scratch on glass?
Fiber Bragg Gratings (FBGs) are not “markings” on the surface, nor are they physical scratches. To answer your questions specifically:
1. Internal vs. External “Markings”
The grating is located inside the core of the optical fiber.
In most OFSCN® products, such as the OFSCN® Polyacrylate Fiber Bragg Gratings or OFSCN® Polyimide Fiber Bragg Gratings, the grating is created by exposing the fiber core to intense ultraviolet (UV) light. This process changes the refractive index of the silica material at a microscopic level. There is no physical etching or material removal on the outside of the glass.
2. Fragility and Structural Integrity
Whether the fiber becomes fragile depends on the manufacturing technique:
- Standard UV Writing: For standard FBGs, the protective coating must be stripped before the UV exposure and then recoated. While the glass itself isn’t “scratched,” the stripping and recoating process can introduced microscopic flaws that slightly reduce the original tensile strength of the fiber compared to a pristine, never-stripped cable.
- Femtosecond Laser Writing: Our OFSCN® Standard Femtosecond Fiber Bragg Gratings are written through the coating. Because the protective layer is never removed, the mechanical strength remains nearly identical to the original fiber.
- High-Strength Requirements: If your application involves high strain or frequent bending, we offer OFSCN® High-Strength Fiber Bragg Gratings, which can withstand strain levels \ge 25,000 \mu\epsilon without breaking.
Unlike a scratch on glass, which creates a stress concentration point on the surface, the “index modulation” of an FBG is internal and does not inherently cause the fiber to become brittle or prone to breaking under normal operating conditions.
Standard Product Visuals:
You can find more technical details on internal structures at www.ofscn.net.