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Historical Facts toward Introduction of Fiber-Optics and Photonics
Published in Tarun Kumar Gangopadhyay, Pathik Kumbhakar, Mrinal Kanti Mandal, Photonics and Fiber Optics, 2019
In the same year, researchers of Bell Laboratory developed a “modified chemical vapour deposition (MCVD)” process. In this system, oxygen and chemical vapors flow to a glass tube and an external heat source is used to heat the chemical vapors to form ultra-transparent silica glass. In this process, the glass preform can be made and later on fiber will be drawn using a fiber-drawing tower. In the MCVD process, reaction takes place within a pure glass tube and selected chemical vapors are passed through it. It is ensured that the required chemical reactions and soot deposition are performed within the close environment so that any foreign ingredients cannot participate in the reaction process. The process also supports mass production of preforms and then low-loss optical fibers [38,39]. This process remains the standard for any commercially fiber production for any length of fiber. Figure 1.4 shows a photograph of a typical MCVD preform fabrication set-up containing ultradry vapor delivery system in the laboratory at CGCRI, Kolkata, India.
Optical Fibers
Published in Le Nguyen Binh, Optical Modulation, 2017
As we have described in previous sections, the standard single mode optical fiber (SSMF) structure is a cylindrical core with a refractive index slightly higher than that of the cladding region. For optical communications operating in the 1300 and 1700 nm wavelength regions, the silica material is the base material. A “pure” silica tube is the starting structure and a combination of silica, gemanimum oxide GeO2 and P2O5, are then deposited inside the tube. Other dopants such as B2O3 and fluoride can also be used to reduce the refractive index of some small regions of the core. Once the deposition of the impurities is done (see Figure 14.17), the tube is collapsed to produce a perform as shown in Figures 14.15 through 14.17. Also shown in these figures is a schematic representation of the fiber drawing machine and fiber drawing tower. The refractive index of the perform is also shown as noted in its caption and its details area in Figure 14.17. Figure 14.18 shows the installation of fiber cables by hanging, by ploughing, for undersea environment . This figure also shows the two optical fibers under splicing to repair a broken or damage fiber strand.
Single- and Few-Mode Structures and Guiding Properties
Published in Le Nguyen Binh, Wireless And Guided Wave Electromagnetics, 2017
Once the deposition of the impurities is done (see Figure 6.15) the tube is collapsed to produce silica preforms as shown in Figure 6.15(a). Also shown in this figure is a schematic of the fiber-drawing machine and fiber-drawing tower. The refractive index of the fiber preform is also shown in this figure, as noted in its caption, and its details are shown in Figure 6.15(b) and (c) and Figure 6.16. The fiber preform is necessary and fabricated by starting with a pure silica tube rotating in a chemical vapor chamber containing the composition of silica and doping impurities for forming the core region. After the deposition of the core material, the silica tube is then collapsed into the preform. This preform is then placed in a drawing tower as shown in Figure 6.17, heated by a microwave section to melting, and drawn into a circular optical waveguide fiber with a control feedback subsystem to ensure the uniformity of the core of the fiber. In addition, the drawn fiber may be spun during the drawing process to obtain uniformity in the fiber core ellipticity to minimize the polarization mode dispersion (PMD), which will be treated in the next chapter. This PMD is very critical for a modern optical fiber system operating at ultra-speed. Figure 6.18 shows the scenarios of installation of fiber cables by aerial hanging, ploughing into the ground and undersea. The PMD is most serious for the aerial environment due to the randomness of wind direction and speeds of the wind and thence the random vibration of the cables.
Low effective Poisson’s ratio and confinement loss photonic crystal fibers using negative Poisson’s ratio air holes structure
Published in Mechanics of Advanced Materials and Structures, 2022
Considered the fabrication method of PCF has become one of the challenging problems, the fabrication feasibility of the proposed PCF is briefly introduced. Since the first elliptical air hole PCF was successfully prepared [40], the fabrication method of PCF has developed rapidly [41, 42]. The current method of PCF fabrication is the stack drawing technique. Firstly, the quartz rods are drawn into elliptical capillary tubes with accurate outer diameter by using the optical fiber drawing tower, then the stacked capillary tubes are placed into a thin-walled quartz tube of the suitable size to make the PCF preform. [43] proposes a fiber quartz rod fabrication method using the ultrasonic drilling machine, which can be used to manufacture complex porous quartz rods. The fabrication process can be carried out after acidifying and heat treatment of the preform. From the simulation results above, the proposed PCF with NPR holes structure has a strong parameter tolerance ability, which makes it can still maintain the reduction effect of macro effective Poisson’s ratio even if the size parameters are not precise during the fabrication, greatly enhancing its application prospect.
Fabrication and characterization of Ge-doped flat fibres
Published in Journal of Modern Optics, 2019
Katrina D. Dambul, Soo Yong Poh, Nizam Tamchek, Din Chai Tee, Fatemeh Amirkhan, Kwok Shien Yeo, Ghafour Amouzad Mahdiraji, Wei Ru Wong, Faisal Rafiq Mahamd Adikan
The flat fibre samples used in this work were fabricated using a fibre drawing tower from an uncollapsed 6 mol% Germanium (Ge)-doped preform. The doped preform was fabricated at the MCVD Lab, Multimedia University, Cyberjaya, Malaysia. The flat fibre was fabricated (drawn) at the Flat Fiber Lab, University of Malaya, Malaysia. The fabrication process starts by melting the preform tube at its melting temperature in a drawing tower furnace. The preform was peripherally heated and drawn along its axial direction (9, 10). Once the neck down occurs, the preform was then pulled down and its drawing conditions such as feed speed and draw speed fulfilled the simplified mass conservation law. When the pulling process occurs at steady state, the governing equation for mass is defined as (11): where r is the radius (m), u is the axial velocity component (m/s), v is the radial velocity component, z is the axial coordinate (m) and ρ is the density (kg/m3). More detailed governing equations for momentum and energy transport can be found in (10). From the conservation of mass, the neck down shape R(z) as illustrated in Figure 2 can be iteratively defined using computational methods as (12): where R1 is the preform outer radius, Uf is the feed speed and Uz is the speed at z. Figure 2 shows the physical model of the neck down profile where R2 is the fibre radius and L is the heating zone length.