Fringe generation with non-uniformly coated long-period fiber gratings

Abstract

In this work, the spectral characteristics of non-uniform symmetrically ring shaped coatings deposited on long-period fiber gratings (LPFGs) have been theoretically and experimentally investigated. To optimize the structure performances, the device was designed with a simulation tool based on vectorial analysis of modes in a multilayer cylindrical waveguide and coupled mode theory. Electrostatic self-assembling technique was selected to deposit with fine control uniform azimuthally symmetric coatings on the cladding of the LPFG. UV laser micromachining operating at 193nm was used to selectively remove the coating with high spatial resolution and with azimuthal symmetry. By locally and selectively removing portions of the overlay surrounding the LPFG from the middle of the grating, strong modifications of its spectral characteristics were observed. Phase-shift effects and multiple interference fringes have been observed for all the attenuation bands, strongly depending on the length of the uncoated region and the overlay features (thickness and optical properties). This provides a valid technological platform for the development of advanced photonic devices for sensing and telecommunication applications.

GeO2 Doped Optical Fiber Plasmonic Sensor for Refractive Index Detection

“…Laser micromachine and side polishing technique can be used to fabricate this kind of structure. The polishing depth can be controlled very well [28][29][30].…”

Fabrication of Phase-Shifted Long-Period Fiber Grating and Its Application to Strain Measurement

“…To date, various methods have been developed to produce a phase shift in a common LPG. In general the phase shift can be permanently inserted into a fiber grating by using either the UV post-processing [8], or the post-writing and -etching techniques [6], [7]. However, all the above methods need either an expensive UV writing system or otherwise a very complicate and time-consuming etching and coating procedures.…”

Power-interrogated and simultaneous measurement of temperature and torsion using paired helical long-period fiber gratings with opposite helicities

“…In the past few decades, long-period fiber grating (LPG) based sensors have been comprehensively studied and have found wide applications in the fields of civil engineering, industry, biomedicine, chemistry, etc [1][2][3][4][5][6][7][8][9]. There are two common interrogation methods that are used for LPG-based fiber sensors: a wavelength-interrogation approach and a power/intensity interrogation approach.…”