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Sensing with Polymer Fiber Bragg Gratings
Published in Ricardo Oliveira, Lúcia Bilro, Rogério Nogueira, Polymer Optical Fiber Bragg Gratings, 2019
Ricardo Oliveira, Lúcia Bilro, Rogério Nogueira
Pressure sensors are important devices in areas ranging from medicine to the oil and gas industry. Monitoring the local variation of pressure allows to prevent leaks in pipelines, which are considered as one of the main threats in the oil and gas industry. Several types of optical fiber sensors have been proposed to measure this parameter using the conventional silica fiber Bragg grating. However, this is a challenging area because of the low compressibility of the silica fiber, which provides inherently low hydrostatic pressure sensitivities (~3–4 pm/MPa) [139,140]. To suppress this problem, the conversion of pressure into strain through special mechanical configurations has been proposed for improving the sensitivity of these fiber optic sensors [141,142]. Yet, the fabrication process could be too elaborate to accomplish.
Active Core Optical Fiber Chemical Sensors and Applications
Published in Krzysztof Iniewski, Ginu Rajan, Krzysztof Iniewski, Optical Fiber Sensors, 2017
The interaction of light guided in an optical fiber core with an analyte or reaction product(s) of an analyte with a sensing reagent inside the optical fiber core is the basis of AC-OFCS using porous solid optical fibers (PSOFs), liquid-core waveguides (LCWs), or hollow waveguides (HWGs) as transducers. In optical fiber industry, the interactions of light guided in an optical fiber with the fiber core materials have also been used for fiber quality control, optical fiber amplifier design, etc. For example, laser-induced optical fiber FL spectroscopy can be used to monitor possible contamination of fiber core material.17 Optical fiber core Raman scattering is another technique having been used to monitor the quality of optical fiber cable.18 The in-fiber amplification technologies significantly improved optical fiber communication capacity. Present in-fiber amplification technologies used in optical fiber communication industry are based on NIR laser-induced FL of erbium ions doped in a silica fiber core.19, 20 Fiber core optical absorption techniques have also been proposed for monitoring high-energy radiation (x-ray, γ-ray) and ionization particles (α-particle, neutron) for applications in nuclear facilities. The irradiation of silica optical fibers by the high-energy radiation and ionization particles breaks down chemical bounds, which causes the generation of radicals, nonbinding oxygen species inside the fiber core. The formed radical species can be detected through monitoring the absorption spectrum of the optical fiber core.21
Optical Fiber Operational Parameters
Published in Le Nguyen Binh, Wireless And Guided Wave Electromagnetics, 2017
In the beginning of the 1980s, there was great interest to reduce the total dispersion [M(λ) + D(λ)] of single-mode optical fiber at 1550 nm, where the loss is lowest for silica fiber. There were two significant trends; one was to reduce the linewidth and stabilize the laser center wavelength, and the other was to reduce the dispersion at this wavelength. The fibers designed for long-haul transmission systems usually exhibit a near-zero dispersion at a certain spectral window. These are dispersion-shifted fibers; that is, at this wavelength we prefer to have the total dispersion = [M(λ) + D(λ)] ∼ 0. The material dispersion factor M(λ) is natural and slightly affected by variation of doping material and concentration. However, the waveguide dispersion factor D(λ), and hence the total dispersion DT(λ), can be tailored by designing appropriate refractive index profiles and geometrical structure to balance the material dispersion effects. Note that the dispersion factors due to material and waveguide take algebraic values; thus, they can be designed to take opposite values to cancel each other. See Appendices 1 and 2 (Sections 7.6 and 7.7) for MATLAB® files as examples for the design of these fibers.
Amphibious sensor of temperature and refractive index based on D-shaped photonic crystal fibre filled with liquid crystal
Published in Liquid Crystals, 2020
Ying Guo, Jianshe Li, Shuguang Li, Yingchao Liu, Xiaojian Meng, Weihong Bi, Huibin Lu, Tonglei Cheng, Rui Hao
Generally, most silica fibres are manufactured by well-known stacking and drawing techniques. Referring to the aperture ratio of the real PCF and selecting the ideal air hole size, a high-birefringence PCF similar to the real fibre is formed on the simulation. The direction in which the double large holes are defined is the y-polarisation direction, and the direction perpendicular thereto is the x polarisation direction. In order to introduce a response-sensitive SPR effect easily, a polishing process is added. For a PCF with a large hole in the core, it is easy to form a bandgap-type light-guiding mechanism under light-passing conditions, and the light of a certain wavelength is trapped in air holes as a core. The introduction of liquid crystal ensures a high refractive index region in the lower air hole and also determines the light-guiding mechanism of total internal reflection for polished fibre. The liquid crystal into the inner air hole selectively is filled by a selective filling technique [33]. Such a capillary was observed under a polarising microscope.