In FBG pigtails, a fiber Bragg grating is integrated in the fiber core to filter certain wavelengths. They are used in sensor multiplexing applications.
FBG fibers are used in fiber optic measurement techniques (e.g., for temperature, pressure, sound, and strain measurements). In data transmission, they are components of wavelength division multiplexing (WDM) systems.
The FBGs are inscribed into the fibers in various ways:
FBGs are inscribed with UV on a standard basis. The coating must first be removed from the fiber core. Following inscription, the FBGs then receive a new coating with a recoater. The biggest advantage of this conventional method is that FBGs are particularly flexible in their spectral design. They are, therefore, used especially in spectrally demanding sensor and telecommunications applications.
Inscribing FBGs into the fiber with a femtosecond laser does not require removal of the coating. Since recoating is not necessary, the great mechanical strength of the fiber is maintained. In addition, the gratings can also be inscribed in non-photosensitive material (e.g., in pure silica fibers, in which the attenuation effects of hydrogen, radiation, and UV are significantly lower).
Femtosecond FBGs, therefore, offer considerable advantages in demanding environmental conditions and are in demand wherever the fiber is subjected to high mechanical stress. They can be found, for example, in the oil and gas industry or in nuclear power plants.
