A new method of fabrication of long-period fiber gratings by twisting of a standard single-mode fiber at high temperature is presented. The method relies on the fact that there always exists some core–cladding eccentricity in the optical fiber. Therefore, when the fiber is twisted, its core follows a helicoidal path inside the cladding. The transmission spectrum of the helicoidal long-period fiber grating that is produced contains several dips that correspond to resonances with the fiber cladding modes.
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