Fiber Bragg Gratings

Fiber Bragg gratings have a periodically altered refractive index to filter certain wavelengths while allowing others to pass. Fiber Bragg gratings (FBGs) are widely used in telecommunication, sensor and laser fields. There are many types of fiber Bragg gratings. Examples include optical fiber Bragg grating, standard fiber Bragg gratings and surface-relief fiber Bragg gratings. In an optical fiber Bragg grating the Bragg exists in the optical fiber and reflects a very narrow bandwidth of light that is centered at the Bragg wavelength in the transmission spectrum. Standard fiber Bragg gratings have periodic modulations in the refractive index of the fiber. Surface-relief fiber Bragg gratings are similar to a standard FBG except fabrication method. Surface-relief fiber Bragg gratings are etched physically into the fiber and enable it to operate at high temperatures. Fiber Bragg grating sensors are used to measure various parameters which introduce a change in reflection wavelength of the FBG. Other fiber Bragg gratings are commonly available.

There are several ways in which fiber Bragg gratings (FBGs) function. Fiber Bragg gratings have low insertion losses and enable low cost manufacturing of high quality wavelength-selective optical devices. An optical fiber Bragg grating operates as a sensor when change in a particular environmental variable like pressure, temperature, or stress are correlated with the shifts in reflected wavelength of the FBG. Some examples of standard fiber Bragg gratings specifications include a center wavelength of 650nm - 1620nm, 90% reflectivity, bandwidth 0.2nm, and fiber length 1.5 meters. Surface-relief Bragg gratings are etched on the cladding above the core of the D-fibers where the interaction remains within evanescent field of the supported fields. Fiber Bragg grating sensors are used to measure parameters such as temperature, strain, pressure, vibration, and acceleration. Fiber Bragg grating sensors can be multiplexed and inherent low transmission loss of 1550 nm. Fiber Bragg gratings (FBGs) are designed and manufactured to meet most industry specifications.

Fiber Bragg gratings are used in many applications. Examples include optical fiber mode converters, wavelength selective filters, multiplexers, spectrum analyzers, and specialized narrowband lasers. Surface-relief fiber Bragg gratings are used in temperature sensing applications and operate until the melting point of glass. Fiber Bragg gratings are provided license by United Technologies Research Center (UTRC) and the Communications Research Centre (CRC).

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