The first in-fiber Bragg grating was demonstrated by Ken Hill in 1978. Initially, the gratings were fabricated using a visible laser propagating along the fiber core. This is achieved by creating a periodic variation in the refractive index of the fiber core, which generates a. The solution came when Charles Kao and George Hockham of the British company Standard Telephones and Cables promoted the idea that the attenuation in the existing optical fibers could be reduced below 20 decibels per kilometer (dB/km), making fibers a practical communication medium. However, it wasn't until the 1990s that FBGs became a widely researched and developed technology. The ability to inscribe intracore Bragg gratings in these photosensitive fibers has revolutionized the field of telecommunications and optical. Bragg gratings are one of the most useful, reliable, versatile, practical, and attractive passive devices in the fields of optical fiber communications and fiber optic sensors.
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