How to caculate Fiber Bragg Grating pitch - grating period Λ

The period of a fiber Bragg grating (FBG) can be calculated using the following formula: where:

• Λ: Grating period - grating pitch
• λ: Wavelength of light in the fiber
• neff: Effective refractive index of light in the fiber

For a fiber Bragg grating with a wavelength of 1550 nm and an effective refractive index of 1.468, the grating period Λ is: ​≈ 528.04nm Therefore, the period of a fiber Bragg grating with a wavelength of 1550 nm is 528 nm.

It is important to note that the effective refractive index of light in a fiber can be affected by factors such as the fiber material, fiber structure, and fiber temperature. Therefore, the actual grating period may be slightly different from the calculated value.

Factors affecting the grating period of a fiber Bragg gratingThe following are some factors that can affect the grating period of a fiber Bragg grating:

• Fiber material: The refractive index of the fiber material will affect the effective refractive index of light in the fiber. Therefore, fiber Bragg gratings made of different fiber materials will have different grating periods.
• Fiber structure: The fiber structure can also affect the effective refractive index of light in the fiber. For example, single-mode and multimode fiber Bragg gratings will have different grating periods.
• Fiber temperature: The fiber temperature can affect the refractive index of the fiber material, which in turn can affect the effective refractive index of light in the fiber. Therefore, changes in fiber temperature will cause changes in the grating period

You can know more in the following URL：

www.ofscn.net/fbg-topics/fbg-and-fbgs.html

www.ofscn.net/fbg-topics/principle.html

www.ofscn.net/fbg-baike/60-principle-02.html