FBG (Fiber Bragg Grating)

An FBG is a periodic modulation of the refractive index created in the core of an optical fiber, which reflects a narrow band of wavelengths (matching the Bragg condition) while transmitting the rest.

How does a Bragg grating work?

The periodic grating structure causes waves reflected from successive planes to interfere constructively only at a precisely defined wavelength (dependent on the grating period and the core's refractive index), which is strongly reflected back along the fiber. The reflected wavelength shifts as the temperature or mechanical strain acting on the fiber changes.

Applications

FBG is the basis for fiber-optic temperature and strain sensors used in structural monitoring of bridges and aircraft, spectral filters in WDM systems, and wavelength-stabilizing elements for fiber lasers.

Related terms

LPG

DTS

WDM