Arc-Induced Long Period Fiber Gratings

Abstract

Long period fiber gratings produced by the electric arc technique have found an increasing interest by the scientific community due to their ease to fabricate, virtually enabling the inscription in any kind of fiber, low cost, and flexibility. In 2005 we have presented the first review on this subject. Since then, important achievements have been reached such as the identification of the mechanisms responsible for gratings formation, the type of symmetry, the conditions to increase fabrication reproducibility, and their inscription in the turning points with grating periods below 200 μm. Several interesting applications in the sensing area, including those sensors working in reflection, have been demonstrated and others are expected, namely, related to the monitoring of extreme temperatures, cryogenic and high temperatures, and high sensitivity refractometric sensors resulting from combining arc-induced gratings in the turning points and the deposition of thin films in the transition region. Therefore, due to its pertinence, in this paper we review the main achievements obtained concerning arc-induced long period fiber gratings, with special focus on the past ten years.

Optical Fibre Long-Period Grating Sensors Operating at and around the Phase Matching Turning Point

“…With increasing wavelength, the cladding mode's effective refractive index will decrease more than the effective refractive index of the core mode [15,30]; this corresponds to the dual bands that become apparent in the LPG transmission spectrum. Figure 4 shows how the grating period of an LPG approaching the turning point of the LP 021 mode affects the transmission spectrum of the LP 020 and LP 021 cladding modes.…”

“…The refractive index can be altered using a number of different methods. Some of these include local exposure of the fibre to a UV laser [28,32,33,34], CO 2 laser [35,36], femtosecond laser [23,37] or by electrical arc discharge [30,38]. PMTPs have been written in conventional single mode and doped fibres [12,11,33,34,36,39], and have been theoretically investigated using photonic crystal fibres [23].…”

Sensing Features of Arc-induced Long Period Gratings

“…As a result, the transmission spectrum of the fiber shows attenuation bands centered at discrete wavelengths, each one corresponding to the coupling between the core mode and a different cladding mode. First demonstrations of gratings were through UV irradiation, nowadays alternative and simpler approaches, based on CO2 lasers and Electric Arc Discharge (EAD) are also proposed, since they enable the inscription in not photosensitive and unconventional fibers as well [1,2]. In the EAD procedure the perturbation is created by applying an electric arc to the fiber with a certain periodicity.…”

“…In the EAD procedure the perturbation is created by applying an electric arc to the fiber with a certain periodicity. Concerning the mechanisms of grating formation, several effects were studied so far, including: dopant diffusion, stress relaxation, geometrical deformations and changes in glass structure [1]. The LPG represents one of the most important fiber grating technological platform that finds wide application for the sensing of physical, chemical and biological parameters [3][4][5].…”

Arc-Induced Long Period Gratings from Standard to Polarization-Maintaining and Photonic Crystal Fibers

“…Different techniques are available for their fabrication, the most important being: UV irradiation [ 9 ], CO 2 lasers [ 32 ], IR femtosecond lasers [ 33 ], mechanical deformations [ 34 , 35 ], and Electric Arc Discharge (EAD) [ 36 , 37 , 38 ]. The UV approach is one of the oldest but is still proposed for photosensitive fibers.…”