Abstract-In this paper we present designs of fibers having non-zero positive, non-zero negative and near-zero ultra-flattened dispersion with small dispersion slope and ultra-large effective area over a wide spectral range. The designs consist of a concentric multilayer segmented core followed by a trench assisted cladding and a thin secondary core. The central segmented core helps in maintaining desired dispersion over a wide range of wavelength. The second core of the fiber helps in achieving ultra-large effective area and trench assisted cladding reduces the bending loss. The designs of the fiber have been analyzed by using the transfer matrix method. For positive non-zero dispersion flattened fiber we have optimized dispersion near +4.5 ps/km/nm in the wavelength range 1.46-1.65 µm. Maximum value of dispersion slope of the fiber in above mentioned wavelength range is 0.026 ps/km/nm 2 . In the design of negative non-zero dispersion flattened fiber, dispersion has been achieved near −6 ps/km/nm in the spectral range of 1.33-1.56 µm and maximum value of dispersion slope is 0.048 ps/km/nm 2 . Dispersion and dispersion slope of near zero dispersion flattened fiber lie in the range [0.0039-0.520] ps/km/nm and [(0.0004)-(0.0365)] ps/km/nm 2 respectively in the spectral range of 1.460-1.625 µm. The near zero dispersion flattened fiber has an ultra-high effective area ranging from 114 µm 2 to 325.95 µm 2 in the aforementioned wavelength range, which covers the entire S+C+L-band. These values of mode area are noticeably higher than those reported in literature for flattened dispersion fibers with large mode area. Designed fiber shows very small bending loss. We report breakthrough in the mode area of the single mode optical fiber with ultra flattened dispersion and low dispersion slope.
This is the accepted version of the paper.This version of the publication may differ from the final published version. Abstract-This paper presents radiation resistant characteristics of fibre Bragg grating (FBG) sensors written in a photosensitive fiber and connected to a silica core radiation resistant optical fibre, aiming to develop a sensor system suitable for both sensing and data transmission in harsh environment. The silica core fluorine-down-doped clad optical fibre has been specifically designed and fabricated for this study using the modified chemical vapor deposition technique. Key waveguide parameters, including the width of the fluorine doped inner cladding have been optimized to obtain a low loss (<0.2 dB/km) at the operating wavelength region of 1550 nm. The fibre fabrication process, mainly the deposition condition, has also been optimized to achieve smooth deposition and sintering of silica core layers, to minimize radiation induced absorption. As a result, radiation induced absorption of ∼2.2 dB/km at 1550 nm under accumulated dose of 25 MRad at dose rate of 0.39 MRad/hr has been successfully achieved. To create an effective sensor system for harsh environmental conditions, this specialty fibre is connected to a number of FBGs (sensors) fabricated in photosensitive fibres prior to their extensive evaluations by being exposed to different accumulated dose of gamma radiation. Their corresponding Bragg wavelength shifts (BWS) and peak amplitudes were continuously monitored. It was found that the radiation induced BWS can be greatly reduced by shielding the sensors using stainless steel tubing. The temperature sensitivity and peak amplitude were found to be largely unchanged before and after exposure to Gamma radiation of 25 MRad which shows their potential use for temperature measurements in radiation environments with an uncertainty of around 0.1°C. Permanent repository link
We report fabrication of a segmented cladding fiber (SCF) in silica-based glass. An SCF with a uniform core of pure silica and cladding of periodically arranged pure silica and fluorine-doped silica in an angular direction has been fabricated by using the stack-and-draw technique. The fabricated fiber has been characterized by capturing its near-field intensity pattern at 633 nm wavelength. The number of modes has been estimated from the captured near-field intensity pattern by using neural network analysis. A four-segment SCF of 30-μm core diameter and 0.43% relative index differences between the high-and low-index segments shows few-mode operation by filtering out higher-order modes of an otherwise highly multimode fiber.
In this paper design of a fiber having ultra-flattened dispersion with small dispersion slope, ultra-large effective area over a wide spectral range has been presented. The segmented core of the fiber helps in achieving large mode field diameter and maintaining very small dispersion over a wide range of wavelengths. The maximum value of dispersion and dispersion slope of the designed fiber is −1.4 ps/km/nm and 0.047 ps/km/nm 2 respectively within the spectral range of 1460-1666 nm. The proposed fiber has ultrahigh effective area ranging from 116 µm 2 to 504 µm 2 in the aforementioned wavelength range, which covers the entire S+C+L-band.
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