Terahertz (THz) band (0.1–10 THz) is the next frontier for ultra-high-speed communication systems. Currently, most of communications research in this spectral range is focused on wireless systems, while waveguide/fiber-based links have been less explored. Although free space communications have several advantages such as convenience in mobility for the end user, as well as easier multi-device interconnectivity in simple environments, fiber-based communications provide superior performance in certain short-range communication applications such as multi-device connectivity in complex geometrical environments (ex., intra-vehicle connectivity) and secure communications with low probability of eavesdropping, as well as secure signal delivery to hard-to-reach or highly protected environments. In this work, we present an in-depth experimental and numerical study of the short-range THz communications links that use subwavelength dielectric fibers for information transmission and define the main challenges and trade-offs in the link implementation. Particularly, we use air or foam-cladded polypropylene-core subwavelength dielectric THz fibers of various diameters (0.57–1.75 mm) to study link performance as a function of the link length of up to ∼10 m, and data bit rates of up to 6 Gbps at the carrier frequency of 128 GHz (2.34 mm wavelength). We find that depending on the fiber diameter, the quality of the transmitted signal is mostly limited either by the modal propagation loss or by the fiber velocity dispersion (GVD). An error-free transmission over 10 m is achieved for the bit rate of 4 Gbps using the fiber of smaller 0.57 mm diameter. Furthermore, since the fields of subwavelength fibers are weakly confined and extend deep into the air cladding, we study the modal field extent outside of the fiber core, as well as fiber bending loss. Finally, the power budget of the rod-in-air subwavelength THz fiber-based links is compared to that of free space communication links, and we demonstrate that fiber links offer an excellent solution for various short-range applications.

中文翻译：

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使用实芯亚波长电介质光纤的色散受限与功率受限的太赫兹传输链路

太赫兹 (THz) 频带（0.1–10 THz）是超高速通信系统的下一个前沿。目前，该光谱范围内的大多数通信研究都集中在无线系统上，而对基于波导/光纤的链路的探索较少。尽管自由空间通信具有多种优势，例如终端用户的移动便利性以及简单环境中更容易的多设备互连，但基于光纤的通信在某些短距离通信应用中提供了卓越的性能，例如多设备连接复杂的几何环境（例如，车内连接）和低窃听概率的安全通信，以及向难以到达或高度受保护的环境安全传输信号。在这项工作中，我们对使用亚波长介电纤维进行信息传输的短距离太赫兹通信链路进行了深入的实验和数值研究，并定义了链路实现中的主要挑战和权衡。特别是，我们使用不同直径（0.57-1.75 mm）的空气或泡沫包覆聚丙烯芯亚波长介电太赫兹光纤来研究链路性能与高达 10 m 的链路长度和高达6 Gbps，载波频率为 128 GHz（2.34 毫米波长）。我们发现，根据光纤直径，传输信号的质量主要受模式传播损耗或光纤速度色散 (GVD) 的限制。使用直径较小的 0.57 mm 光纤，以 4 Gbps 的比特率实现超过 10 m 的无差错传输。此外，由于亚波长光纤的场被弱限制并深入空气包层，我们研究了光纤纤芯外的模场范围以及光纤弯曲损耗。最后，将空中棒状亚波长 THz 光纤链路的功率预算与自由空间通信链路的功率预算进行比较，我们证明光纤链路为各种短距离应用提供了出色的解决方案。