Long period fiber gratings with off-resonance spectral response based on mechanical oscillations.

We present long period fiber gratings with off-resonance spectral response. Our long period fiber gratings are created by the periodic structure of large perturbations in the fiber diameter. These perturbations result in unique spectral response, even in off-resonance frequencies. Writing these long period fiber gratings is based on utilizing the mechanical vibrations of tapered fibers during the tapering process. This writing method is simple and robust; it has high efficiency, high reproducibility, and low polarization dependency; and it enables real-time tunability of the periodicity, efficiency, and length of the grating. We also demonstrate a complex grating by writing multiple gratings one on top of the other. Finally, we utilize the formation of the gratings in different fiber diameters to investigate the Young's modulus of tapered fibers.