Long period grating has a wide variety of applications, including band-rejection filters, gain flattening filter and sensors. Various gratings with complex structures have been designed: gratings combining several LPFGs, LPFGs with superstructures, chirped gratings, and gratings. Microbend gratings, which are antisymmetric with respect to the fiber axis, create a resonance between the core mode and the asymmetric LP1m modes of the core and the cladding. As a band rejection filter, all light in a spectral slice is discarded without affecting the amplitude and phase of neighbouring wavelengths, with the additional advantage of low insertion losses. Structure-Modulated Long-Period Fiber Gratings (SM-LPFGs) represent an advancement in fiber optic sensor technology, moving beyond traditional photosensitivity-based fabrication to achieve enhanced performance through the direct physical modification of the geometry of the fiber. This review. In this work, we reviewed the most important achievements of INESC TEC related to the fabrication of long-period fiber gratings using the electric arc technique. We focused on the fabrication setup, the type of fiber used, and the effect of the fabrication parameters on the gratings' transmission. The photonic crystal fiber (PCF) is a special class of components incorporating photonic crystals with a two-dimensional (2D) periodic variation in the plane perpendicular to the fiber axis and an invariant structure along it [1-3]. Typically these fibers incorporate a number of air holes that form. A long-period grating is obtained by introducing a periodic refractive index modulation in the core of a hydrogen-sensitized germanosilicate fiber. The phase-matching condition causes light from the fundamental guided mode to couple to discrete, forward-propagating cladding modes.