Abstract

Abstract

Abstract

Abstract
In this work is studied the response of optical fiber long period grating (LPG) to changes of the refractive index of the external media relatively to variations of wavelength and in transmission. The response of the LPG to refractive index greater and lesser than to cladding is investigated. A nanolayer was deposited onto the fiber to increase the sensitivity of the LPG to refractive index of the external media higher than cladding. The film modifies the rates of effective modes of cladding, thus improving the response of the changes in the refractive index of the external media higher than that in the refractive index of the cladding (n(cl) approximate to 1.457). The Langmuir-Blodgett technique was used for the deposition of the nanolayer.

Abstract
Optical coherence tomography (OCT) imaging at the 1060-nm region proved to be a successful alternative in ophthalmology not only for resolving intraretinal layers, but also for enabling sufficient penetration to monitor the subretinal vasculature in the choroid when compared to most commonly used OCT imaging systems at the 800-nm region. To encourage further clinical research at this particular wavelength, we have developed a compact fiber-optic source based on amplified spontaneous emission (ASE) centered at similar to 1060 nm with similar to 70-nm spectral bandwidth at full-width at half-maximum and output power > 20 mW. Our approach is based on a combination of slightly shifted ASE emission spectra from a combination of Neodymium- and Ytterbium-doped fibers. Spectral shaping and power optimization have been achieved using in-fiber filtering schemes. We have tested the performance of the source in an OCT system optimized for this wavelength.

Abstract
The analysis of the quality of food oils is of paramount importance because the degradation of oils can lead to formation of harmful substances to the human organism With the increase of the degradation of oils an increase of its refractive index occurs The objective of this work is to develop and to characterize optical fiber refractometers sensitive to variations of refractive index of food oil samples The optical fiber refractometers thanks to the intrinsic characteristics make them suitable for monitoring the quality of frying oils They possess the advantages to require small volumes of sample for analysis do not contaminate the sample and supply the response in real time In this work a long period grating (LPG) as refractometer is used because of their sensitivity to refractive index of the external media degraded and not degraded frying oil samples The oil samples had been characterized by the analysis of total polar components The refractive index of oil is above 1 47 this region the LPG does not show enough sensitivity a nanolayer of an organic material was coated onto the fiber Using the Langmuir-Blodgett technique the response of LPG is modified according to the refractive index and thickness of the film (he deposition of the film modifies the rates effective modes of cladding thus improving the response of the changes in the refractive index of the external media higher than that the refractive index of the cladding (n = 1 457)