Is the spacing of the internal “fences” exactly the same throughout? Is this the most commonly used type of grating?
A Uniform Grating (specifically a Uniform Fiber Bragg Grating or Uniform FBG) is the most fundamental type of fiber optic grating. To answer your questions directly:
1. Is the spacing exactly the same throughout?
Yes. In a uniform grating, the grating period (\Lambda)—which you referred to as the spacing of the internal “fences”—is constant along the entire longitudinal axis of the fiber core. Additionally, the refractive index modulation depth is also uniform.
Because the spacing is consistent, it reflects a very specific, narrow wavelength of light (the Bragg wavelength) according to the formula:
\lambda_B = 2 \cdot n_{eff} \cdot \Lambda
(Where \lambda_B is the reflected wavelength, n_{eff} is the effective refractive index, and \Lambda is the grating period.)
2. Is this the most commonly used type of grating?
Yes, it is the most widely used type in the industry. Most standard OFSCN® FBG sensors for temperature and strain measurement utilize uniform gratings because they provide a clear, sharp reflection peak that is easy for a demodulator (interrogator) to track.
Standard Product Mapping
At OFSCN (Beijing Dacheng Yongsheng Technology Co., Ltd.), we use high-quality uniform gratings as the “sensing element” inside our specialized protective housings. For example:
- OFSCN® 300°C Fiber Bragg Grating Temperature Sensor: Uses uniform FBGs encapsulated in seamless stainless steel tubes for precise thermal monitoring.
- OFSCN® FBG Strain Sensor (Alloy Tube Packaged): Utilizes uniform FBGs to detect micro-strains in harsh environments.
Visual Representation of a Uniform FBG:
https://www.ofscn.net/images/fbg/fbg-structure-principle.jpg
While there are “Chirped Gratings” (where the spacing changes) and “Apodized Gratings” (where the strength changes), the Uniform Grating remains the industry standard for general sensing due to its reliability and predictable mathematical behavior.
If you have a specific application in mind, such as high-speed sensing or extreme temperature monitoring, please feel free to share the environment details.