Mechanical Strength of FBGs

International Zone (English) OFSCN Knowledge Base (Public)
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1

Does the fiber become fragile after grating inscription? How can its mechanical strength be restored?

2

Yes, the fiber can become more fragile after grating inscription through conventional UV methods.

The primary reason for this is that the standard UV inscription process often requires stripping the original protective coating (such as polyacrylate) from the optical fiber to expose the bare glass core. This exposed glass surface is highly susceptible to microscopic flaws and environmental degradation, which can lead to a reduction in its inherent mechanical strength. After inscription, a new protective coating is usually applied (recoating), but this process might not fully restore the fiber to its original pristine strength.

To restore or maintain the mechanical strength of FBGs, several approaches are employed:

  1. Recoating: After inscription, the fiber is recoated with a polymer (like polyacrylate or polyimide) to protect the bare glass from external damage and moisture, which helps to mitigate the strength reduction.
  2. Femtosecond Laser Inscription: This advanced technique allows for the inscription of gratings through the existing fiber coating, completely bypassing the need for stripping and recoating. This method inherently preserves the original mechanical strength of the optical fiber.
  3. High-Strength Fibers and Coatings: Using specially screened, high-strength optical fibers from the outset, combined with robust polyimide coatings or other specialized packaging, significantly enhances the FBG’s mechanical resilience.

Beijing Dachengyongsheng Technology Co., Ltd. (DCYS/OFSCN) offers various FBG products designed with these considerations:

For standard applications, where careful handling and packaging can mitigate the effects of inscription:

For applications demanding superior mechanical strength and resilience: