Fiber Bragg Grating

What Does Fiber Bragg Grating Mean?

Fiber Bragg Grating (FBG) is a simple and low-cost filter built into the core of a wavelength-specific fiber cable. FBGs are used as inline optical filters to block certain wavelengths, or as wavelength-specific reflectors.


Implemented in the 1990s, FBGs improve optical signal quality and are key to fiber optic construction. FBGs also may be used to stabilize laser output.

Techopedia Explains Fiber Bragg Grating

A FBG is created by using an intense ultraviolet (UV) source to write a systematic (periodic or aperiodic) refractive index variations into an optical fiber core. As light moves along the fiber and encounters refractive index changes, a small amount of light is reflected at each boundary. When the grating and light wavelength period are the same, positive reinforcement is provided via power that is coupled from forward to backward directions. Light from other wavelengths cannot propagate, due to out-of-phase reflection interference.

The three most common FBG types are:

  • Uniform FBG: Uniform grating periods are used.
  • Chirped FBG: Variable grating periods are written into the core.
  • Blazed FBG: Constructed when grating is written at an oblique angle to the core’s center axis.

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Margaret Rouse

Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…