Fabrication of a Low-Loss Fused Fiber Spatial-Mode Coupler for Few-Mode Transmission

Abstract

Spatial-mode couplers (SMCs) are critical devices for mode-division- multiplexed (MDM) systems. In this letter, we report a low-loss symmetric SMC fabricated with custom-designed two-mode fiber and commercially available standard fused biconical taper station. Sophisticated hydrofluoric etching or pre-pulling on the fiber sample is not needed for fabrication. We characterize the performance of the fabricated SMC, which shows a low loss of 1.1-2 dB and high modal extinction ratio of >20dB for a broad wavelength range from 1539 to 1555 nm. We demonstrate transmission of 69.2-Gb/s LP01/LP1111 dual-mode MDM coherent optical orthogonal-frequency division multiplexing signal over 4.5-km two-mode f..