3D-Printed Terahertz Subwavelength Dual-Core Fibers With Dense Channel-Integration

Terahertz (THz) fiber that provides high-speed connections is one of the most essential components in THz communication systems. The emerging space-division-multiplexing technology is expected to increase the transmission capacity of THz communications. A promising candidate to achieve that is integrating multiple channels in a compact THz multi-core fiber system. Here, we propose and experimentally demonstrate a THz subwavelength rectangular dielectric dual-core fiber structure, where two identical cores can be densely integrated, thanks to the polarization-maintaining feature of the rectangular fiber. Different configurations of the fiber structure, including the placements, core-spacings, and polarization states of two fiber cores, are comprehensively investigated to improve the channel isolation. Numerical simulations show that the fractional power in core of fiber mode has a dominant effect on inter-core coupling performance. Moreover, we design the core size (1 mm × 0.5 mm) slightly less than the WR5.1 waveguide (1.295 mm × 0.6475 mm) so that the fiber can be conveniently connected with the WR5.1 flange port with mode excitation efficiencies up to 62.8%. A cost-efficient dielectric 3D printing technique is employed for rapid fabrications of dual-core fibers as well as corresponding polymer flange structures that offer solid integration between the fiber samples and the WR5.1 port. Experimental measurements of dual-core fibers demonstrate that a 4-mm core-spacing (less than three times of the operation wavelengths over a frequency range of 0.17–0.21 THz) is sufficient to support robust dual-channel propagation with channel isolation values more than 15 dB, which are consistent with the theoretical and numerical results. This work provides a densely integrated dual-core fiber system with low fabrication cost and practical connection to WR5.1 flange, holding exciting potentials for high-capacity THz space-division-multiplexing communication systems.