“…Higher-order modes have some special optical properties and applications; however, in many areas of the modern science and technology, stable single-mode operation in waveguide is a fundamental requirement, such as high performance fiber laser, sensors, photolithography, and optical coherent tomography systems [14,15]. For conventional communication fiber, there are many ways to filter higher-order modes at wavelength shorter than the cutoff wavelength of the optical fiber, such as sub-wavelength optical wires (SOWs) [16][17][18][19] and micro fiber coupler [20]. For largemode-area fiber, the coiling technique [21] is widely used.…”