Abstract
We propose a ring-core photonic quasi-crystal fiber (RC-PQCF) featuring a ring-shaped fiber core and two symmetrical SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> stress-applying parts (SAPs). By optimizing the mole percentage of GeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and geometrical parameters of the fiber, the design supports 34 full vector polarization modes (FV-PMs). The effective refractive index difference ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta {n_{eff}}$</tex-math></inline-formula> ) of adjacent FV-PMs is larger than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1.07 \times {10^{ - 4}}$</tex-math></inline-formula> at 1550 nm. The confinement loss ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\mathrm{\alpha }}$</tex-math></inline-formula> ) of FV-PMs is less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${10^{ - 6}}$</tex-math></inline-formula> , which is sufficient to confine the light field in the ring-core. Through numerical analysis, broadband performance is investigated subsequently in the 1500–1600 nm. The dispersion ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${D_\lambda }$</tex-math></inline-formula> ) of FV-PMs is less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$138.14{\mathrm{\ ps}} \cdot {\mathrm{n}}{{\mathrm{m}}^{ - 1}} \cdot {\mathrm{k}}{{\mathrm{m}}^{ - 1}}$</tex-math></inline-formula> and maintains a flat trend. The mode field area ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${A_{eff}}$</tex-math></inline-formula> ) of FV-PMs is larger compared to single mode fibers and the nonlinear coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\mathrm{\gamma }}$</tex-math></inline-formula> ) of FV-PMs is within ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$6.97 \times {10^{ - 4}}$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1.54 \times {10^{ - 3}}$</tex-math></inline-formula> ) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\mathrm{m}}^{ - 1}} \cdot {{\mathrm{W}}^{ - 1}}{\mathrm{\ }}$</tex-math></inline-formula> in the 1500–1600 nm. The fiber is a promising design for mode division multiplexing (MDM) that supports the MIMO-free processing and improves the transmission capacity and spectral efficiency.
Highlights
WITH the forthcoming capacity crunch of optical fiber communication system, mode division multiplexing (MDM) techniques have attracted great attention [1]
Based on mature multiplexing technologies such as timedivision multiplexing (TDM), wavelength-division multiplexing (WDM) and space-division multiplexing (SDM) [2]–[4], MDM using different types of fiber modes provides another degree of freedom to increase the transmission capacity
Due to the higher refractive index contrast and the good design flexibility, it is more convenient for PCFs to realize full vector polarization modes (FV-PMs)
Summary
WITH the forthcoming capacity crunch of optical fiber communication system, mode division multiplexing (MDM) techniques have attracted great attention [1]. In 2017, researchers presented a PANDA ring-core fiber with 10 polarizationmaintaining modes [24] It has a ring-shaped fiber core with two SPAs. In the same year, a polarization-maintaining supermode fiber with quasi-elliptically arranged high refractive index cores was proposed in Ref [26]. A polarization-maintaining supermode fiber with quasi-elliptically arranged high refractive index cores was proposed in Ref [26] This design supports 20 polarization modes and holds better manufacturing flexibility. In 2018, Wang et al designed a PANDA-type elliptical-core multimode fiber supporting 24 fully lifted eigenmodes [19]. Due to the higher refractive index contrast and the good design flexibility, it is more convenient for PCFs to realize FV-PMs. In 2019, a photonic crystal fiber supporting fully separated eigenmodes was proposed [27]. The simulation is performed in a full-vector finite-element mode solver with a perfect matching layer (PML) as the boundary condition
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