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Fiber Bragg Gratings (FBG)

What is a Fiber Bragg Grating?

A fiber Bragg grating is periodic variation in the refractive index in a small section of optical fiber . As light propagates along the fiber a very narrow range of wavelengths is reflected by the Bragg grating, while all other wavelengths are transmitted through the grating. The center of this reflected band is called the Bragg wavelength.

Bragg Grating Calculator

  1. FBG Diagrams

Uses of Fiber Bragg Gratings

Because the Bragg wavelength can be affected by external stimuli, Fiber Bragg gratings are useful in creation of low insertion loss optical sensors. These sensors are light weight and have the same dimensions as the optical fiber. They are also inert to electromagnetic interference. Fiber Bragg grating sensors can be used as strain gauges in civil structures and aircraft. Other uses include chemical, temperature and pressure monitoring in a variety of applications where traditional sensors might not be desirable.
Fiber Bragg Gratings are widely used as strain gauges. Under stress, the period of a FBG increases due to the physical stretching of the optical fiber. This change results in a shift in the Bragg wavelength. Similarly, temperature sensors make use of thermal expansion to change the grating period. In chemical sensing the Fiber Bragg grating is coated with a polymer, and as chemicals diffuse into the polymer the average refractive index of the grating changes shifting the Bragg wavelength.

  1. Strain Diagram

  1. Fabrication of Standard Fiber Bragg Gratings

Surface-Relief Bragg Gratings

We have recognized the functionality of standard fiber Bragg gratings and are currently researching the realm of surface-relief fiber Bragg gratings (SR-FBG) where the diffraction pattern is physically etched into the structure of the fiber. In this research we are seeking to implement Bragg gratings on a fiber that are more robust and durable in harsh environments of elevated temperatures. Go here to learn more about our research in surface-relief fiber Bragg gratings:

Surface-Relief Bragg Gratings

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